BSB BANCORP INC
8-K, 2000-04-28
STATE COMMERCIAL BANKS
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<PAGE>   1

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM 8-K

                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       the Securities Exchange Act of 1934

        Date of Report (Date of earliest event reported): April 19, 2000

                                BSB BANCORP, INC.
             ------------------------------------------------------
             (Exact name of registrant as specified in its charter)

Delaware                     0-17177                   16-1327860
- --------------------------------------------------------------------------------
(State or other              (Commission               (IRS Employer
jurisdiction of              File Number)              Identification No.)
incorporation)

       58-68 Exchange Street, Binghamton, New York               13901
       ---------------------------------------------------------------
       (Address of principal executive offices)             (Zip Code)

Registrant's telephone number, including area code:  (607) 779-2525
                                                     --------------

                                 Not Applicable
          -------------------------------------------------------------
          (Former name or former address, if changed since last report)


<PAGE>   2


ITEM 1.  CHANGES IN CONTROL OF REGISTRANT.

                  On April 20, 2000, BSB Bancorp, Inc., a Delaware corporation
("BSB Bancorp") announced that it had entered into an Agreement and Plan of
Merger (the "Agreement") with NBT Bancorp Inc., a Delaware corporation ("NBT
Bancorp"), which provides for the merger of NBT Bancorp and BSB Bancorp in a
tax-free, stock-for-stock exchange (the "Merger"). The Merger is subject to
certain conditions, including the approval by the BSB Bancorp and NBT Bancorp
shareholders and the receipt of the required regulatory approvals. In connection
with the Agreement, BSB Bancorp and NBT Bancorp entered into Option Agreements
(the "Option Agreements") pursuant to which each side granted the other side
options, exercisable under certain circumstances, to purchase fully paid and
nonassessable shares of their respective common stock in an amount equal to
19.9% of the total number of outstanding shares of either BSB Bancorp's or NBT
Bancorp's common stock as of the day the options become exercisable. Pursuant to
the Merger Agreement, BSB Bank & Trust Company ("BSB Bank"), a wholly owned
subsidiary of BSB Bancorp will also merge with NBT Bank, National Association, a
wholly owned subsidiary of NBT Bancorp.

                  The Agreement (including Exhibits thereto) and the Option
Agreements are attached hereto as Exhibit 2.1, Exhibit 2.2 and Exhibit 2.3,
respectively, and are incorporated by reference herein.

ITEM 7.           FINANCIAL STATEMENTS AND EXHIBITS.

         (a)    Not applicable.

         (b)    Pro forma financial information

                Not applicable.

         (c)    Exhibits

                  2.1      Agreement and Plan of Merger, dated as of April 19,
                           2000, by and between NBT Bancorp Inc. and BSB
                           Bancorp, Inc.

                  2.2      BSB Option Agreement, dated as of April 19, 2000, by
                           and between BSB Bancorp, Inc. and NBT Bancorp Inc.
                           (filed as an attachment to Exhibit 2.1)

                  2.3      NBT Option Agreement, dated as of April 19, 2000, by
                           and between NBT Bancorp Inc. and BSB Bancorp, Inc.
                           (filed as an attachment to Exhibit 2.1)


<PAGE>   3

                                   SIGNATURES

                  Pursuant to the requirements of the Securities Exchange Act of
1934, the Registrant has duly caused this report to be signed on its behalf by
the undersigned thereunto duly authorized.

                                 BSB BANCORP, INC.
                                 (Registrant)


Date:  April 27, 2000            By: /s/ Thomas L. Thorn
                                    ------------------------------
                                    Thomas L. Thorn
                                    Acting President and Chief Executive Officer


<PAGE>   4


                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
Exhibit No.                         Description                                         Page
- -----------                         -----------                                         ----
<S>               <C>                                                                   <C>
2.1               Agreement and Plan of Merger, dated as of April 20, 2000, by
                  and between NBT Bancorp Inc. and BSB Bancorp, Inc.

2.2               BSB Option Agreement, dated as of April 19, 2000, by and
                  between BSB Bancorp, Inc. and NBT Bancorp Inc. (filed as an
                  attachment to Exhibit 2.1)

2.3               NBT Option Agreement, dated as of April 19, 2000, by and
                  between NBT Bancorp Inc. and BSB Bancorp, Inc. (filed as an
                  attachment to Exhibit 2.1)
</TABLE>

<PAGE>   1
                                                                     EXHIBIT 2.1


                          AGREEMENT AND PLAN OF MERGER

                  AGREEMENT AND PLAN OF MERGER, dated as of April 19, 2000 (this
"Agreement"), by and between NBT BANCORP INC, a Delaware corporation ("NBT"),
and BSB BANCORP, INC, a Delaware corporation ("BSB") (at times, referred to
herein as the "Party" or the "Parties").

                              W I T N E S S E T H:

                  WHEREAS, NBT is a registered bank holding company with the
Board of Governors of the Federal Reserve System ("FRB") under the Bank Holding
Company Act of 1956, as amended (the "BHCA"); and

                  WHEREAS, BSB is a registered bank holding company with the FRB
under the BHCA; and

                  WHEREAS, the Boards of Directors of NBT and BSB have
determined it is advisable and in the best interests of their respective
companies and stockholders to consummate the business combination transaction
provided for herein in which BSB will, subject to the terms and conditions set
forth herein, merge with and into NBT, with NBT being the Surviving Corporation
(as hereinafter defined) (the "Merger"); and

                  WHEREAS, prior to consummation of the Merger, NBT and BSB will
cause BSB Bank & Trust Company, a New York-chartered commercial bank and trust
company headquartered in Binghamton, New York and wholly owned subsidiary of BSB
("BSB Bank"), and NBT Bank, National Association, a national banking association
headquartered in Norwich, New York and wholly owned subsidiary of NBT ("NBT
Bank"), to enter into a bank plan of merger, in the form attached hereto as
Exhibit A (the "Bank Merger Agreement"), providing for the merger of BSB Bank
with and into NBT Bank (the "Bank Merger"), with NBT Bank being the resulting
bank of the Bank Merger (the "Resulting Bank"), and it is intended that the Bank
Merger be consummated immediately after consummation of the Merger; and

                  WHEREAS, in order to effect the aforementioned combination,
the respective Boards of Directors of NBT and BSB have (i) determined in
accordance with the General Corporation Law of the State of Delaware ("Delaware
Law") that the Merger, pursuant and subject to the terms and conditions of this
Agreement, is advisable and in the best interests of their respective
corporations and their stockholders, and (ii) adopted a resolution approving
this Agreement and the other transactions contemplated hereby; and

                  WHEREAS, the Board of Directors of NBT has resolved to
recommend approval of this Agreement and the Merger by the stockholders of NBT;
and
<PAGE>   2

                  WHEREAS, the Board of Directors of BSB has resolved to
recommend approval of this Agreement and the Merger by the stockholders of BSB;
and

                  WHEREAS, NBT and BSB intend to effect a merger that qualifies
for pooling of interests accounting treatment and that qualifies as a
reorganization under Section 368(a) of the Internal Revenue Code of 1986, as
amended (the "Code") with this Agreement representing the plan of reorganization
for purposes of the Code; and

                  WHEREAS, as a condition and inducement to NBT to enter into
this Agreement, BSB will enter into a stock option agreement in the form
attached hereto as Exhibit B (the "BSB Stock Option Agreement"); and

                  WHEREAS, as a condition and inducement to BSB to enter into
this Agreement, NBT will enter into a stock option agreement in the form
attached hereto as Exhibit C (the "NBT Stock Option Agreement"); and

                  WHEREAS the Parties desire to make certain representations,
warranties and agreements in connection with the Merger and also to prescribe
certain conditions to the Merger;

                  NOW, THEREFORE, in consideration of the foregoing and the
mutual covenants and agreements herein contained, and intending to be legally
bound hereby, the Parties hereby agree as follows:

                                    ARTICLE I

                                   THE MERGER

                  SECTION 1.01.  The Merger.

                  Subject to the terms and conditions of this Agreement, in
accordance with Delaware Law, at the Effective Time (as defined in Section 1.02)
BSB shall merge with and into NBT. As a result of the Merger, the separate
corporate existence of BSB shall cease and NBT will continue as the surviving
corporation of the Merger (the "Surviving Corporation").

                  SECTION 1.02.  Effective Time.

                  The Merger shall become effective on the date and at the time
specified in the Certificate of Merger (the "Certificate of Merger") in
substantially the form attached as Exhibit D hereto, as filed with the Secretary
of State of the State of Delaware (the date and time so specified in the
Certificate of Merger is hereinafter referred to as the "Effective Time").

                  SECTION 1.03.  Effect of the Merger.

                           (a)      Legal Effect. At and after the Effective
Time, the Merger shall have the effects set forth in Sections 259 and 261 of
Delaware Law.


                                       2
<PAGE>   3

                           (b)      Name Changes. The names of the Surviving
Corporation and the Resulting Bank shall be changed at the Effective Time to new
names to be determined by mutual agreement of the Parties within 45 days after
the execution of this Agreement; provided that neither the Surviving
Corporation's new name nor the Resulting Bank's new name shall include "NBT" or
"BSB."

                           (c)      Post-Merger Operations. Upon the Merger,
the Parties intend that the headquarters and principal offices of the Surviving
Corporation will be in Binghamton, New York. It is further anticipated that the
Surviving Corporation and its subsidiaries will, for the foreseeable future,
maintain significant operations in Chenango and Oneida Counties, New York and in
Lackawanna County, Pennsylvania.

                  SECTION 1.04.  Certificate of Incorporation and Bylaws.

                           (a)      At the Effective Time, the Certificate of
Incorporation, as amended, of NBT in effect immediately prior to the Effective
Time shall be amended in the Merger by (i) amending Article FIRST thereof to
reflect the new name of the Surviving Corporation and by (ii) amending Article
FOURTH thereof to read as follows:

                  "FOURTH: The total number of shares of all classes of stock
                  which the Corporation shall have the authority to issue is One
                  Hundred Five Million (105,000,000) shares, consisting of One
                  Hundred Million (100,000,000) shares of Common Stock having a
                  par value of $.01 per share and Five Million (5,000,000)
                  shares of Preferred Stock having a par value of $.01 per
                  share."

As so amended, the Certificate of Incorporation of NBT shall be the Certificate
of Incorporation of the Surviving Corporation. At the Effective Time, the Bylaws
of NBT in effect immediately prior to the Effective Time shall become the Bylaws
of the Surviving Corporation, except that the Bylaws shall be revised to reflect
the new name of the Surviving Corporation.

                           (b)      At the Effective Time, the Certificate of
Organization, Articles of Association and Bylaws of NBT Bank in effect
immediately prior to the Effective Time shall become the Certificate of
Organization, Articles of Association and Bylaws of the Resulting Bank, except
that such organizational documents shall be amended to reflect the new name of
the Resulting Bank.

                  SECTION 1.05.  Senior Executive Officers..

                  At the Effective Time, the persons listed in Exhibit E
attached hereto shall serve as the senior executive officers of the Surviving
Corporation and the senior executive officers of the Resulting Bank in the
capacities noted opposite their respective names.

                  SECTION 1.06.  Representation on the Board of the Surviving
                  Corporation

                           (a)      (i) If the proposed acquisition of Pioneer
American Holding Company Corp. ("Pioneer") by NBT is consummated prior to the
Effective Time, at the Effective Time, the board of directors of the Surviving
Corporation shall consist of 15


                                       3
<PAGE>   4

directors, seven of whom shall be designated by BSB's board of directors and six
of whom shall be designated by NBT's board of directors from among the existing
membership of their respective boards of directors immediately prior to the
Effective Time. In designating these directors, each of BSB and NBT shall
allocate those directors to Class 1, Class 2 and Class 3 as equally as possible.
In addition, NBT shall designate one director, from among the former members of
the board of directors of Lake Ariel Bancorp, Inc. (the "Former Lake Members")
who are serving on the board of NBT at the Effective Time. If there are no such
Former Lake Members, NBT shall designate another Former Lake Member. NBT shall
also designate one director from among the former members of the board of
directors of Pioneer (the "Former Pioneer Members") who are serving on the Board
of NBT at the Effective Time. If there are no such Former Pioneer Members at the
Effective Time, NBT shall designate another Former Pioneer Member. The Former
Lake Member and the Former Pioneer Member so designated shall become directors
of the Surviving Corporation and shall be allocated to the classes on the board
of directors as equally as possible. (ii) If the proposed acquisition of Pioneer
is not consummated prior to the Effective Time, the board of directors of the
Surviving Corporation shall consist of 13 directors, six of whom shall be
designated by BSB's board of directors, six of whom shall be designated by NBT's
board of directors and one Former Lake Member designated by NBT who is serving
on the Board of NBT at the Effective Time. If there are no such Former Lake
Members, NBT shall designate another Former Lake Member. The directors
designated by each of BSB and NBT shall be allocated to classes as equally as
possible. (iii) The selections to be made pursuant to this Section 1.06(a) shall
be made no later than 20 Business Days following the date of this Agreement and
shall be noted on Schedule 1.06(a) to be attached to and deemed a part of this
Agreement. It is agreed that if any individual so designated shall be unable or
unwilling to serve as a director of the Surviving Corporation at the Effective
Time, the party that designated such individual shall designate another
individual, who was eligible under this Section 1.06(a) to have been so
designated on or before 20 Business Days following the date of this Agreement,
to serve in such individual's place. If no other individual is so eligible, then
the size of the board of directors of the Surviving Corporation shall be reduced
by one. BSB and NBT agree to establish within 20 Business Days following the
date of this Agreement transition committees to be comprised of the individuals
designated to serve on the Board of Directors of the Surviving Corporation
("Transition Committees") and such Transition Committees shall meet periodically
at times to be decided by mutual agreement of BSB and NBT until the Effective
Date.

                           (b)      It is agreed that the composition of the
board of directors of the Surviving Corporation outlined in paragraph (a) of
this Section 1.06 implements an interim program that will change over time as
the board of directors of the Surviving Corporation is expanded to include
persons who are not currently directors of NBT, BSB, or Pioneer and whose
membership on the board of directors of the Surviving Corporation will afford
representation to communities within the present and prospective service area of
the Surviving Corporation which are not currently represented on the board of
directors of the Surviving Corporation.

                           (c)      The initial chairmanships of the committees
of the Board of Directors of the Surviving Corporation shall be as set forth in
Schedule 1.06(c), to be attached and deemed a part of this Agreement.


                                       4
<PAGE>   5

                  SECTION 1.07   Composition of the Board of the Resulting Bank

                  At the Effective Time, the board of directors of the Resulting
Bank shall consist of the chairman of the board of directors of the Surviving
Corporation, who shall serve as the chairman of the board of the Resulting Bank,
and eight, ten or twelve other persons, half of whom will be designated by NBT
and half of whom will be designated by BSB. The number of such other persons
shall be agreed upon by NBT and BSB, and in the absence of timely agreement such
number shall be set at ten. The number of directors and the selection of
directors to be designated by NBT and BSB under this paragraph shall be
determined and made no later than 20 Business Days following the date of this
Agreement and shall be noted on Schedule 1.07 to be attached to and deemed a
part of this Agreement, provided, that the president of the Resulting Bank shall
be one of the directors so designated by NBT.

                  SECTION 1.08.  Conversion of Common Stock.

                  At the Effective Time, by virtue of the Merger and without any
action on the part of NBT, BSB, or the holders of any of the following
securities:

                           (a)      Each share of BSB common stock, par value
$.01 per share ("BSB Common Stock") (all such shares of BSB Common Stock being
hereinafter collectively referred to as the "Shares") issued and outstanding
immediately prior to the Effective Time (other than any Shares to be cancelled
pursuant to Section 1.8(b)) shall, by virtue of this Agreement and without any
action on the part of the holder thereof, be converted, in accordance with
Section 1.09, into the right to receive two shares, as may be adjusted as
provided elsewhere herein, of NBT common stock, par value $.01 per share ("NBT
Common Stock") (the "Exchange Ratio"). As of the Effective Time, all such Shares
shall no longer be outstanding and shall automatically be cancelled and retired
and shall cease to exist, and each certificate previously representing any such
Shares shall thereafter represent the right to receive a certificate
representing shares of NBT Common Stock into which such Shares are convertible.
For the purposes of this Agreement, references to BSB Common Stock shall be
deemed to include, where appropriate, references to the right to receive shares
of BSB Series A Junior Participating Preferred Stock pursuant to the Rights
Agreement, dated as of May 24, 1999, as amended between BSB and American Stock
Transfer & Trust Company ("AST") (the "BSB Rights Agreement"). Certificates
previously representing Shares shall be exchanged for certificates representing
whole shares of NBT Common Stock issued in consideration therefor upon the
surrender of such certificates in accordance with the provisions of Section
1.09, without interest. No fractional shares of NBT Common Stock shall be
issued, and, in lieu thereof, a cash payment shall be made pursuant to Section
1.09 hereof.

                           (b) Each Share held in the treasury of BSB and each
Share owned by NBT or any direct or indirect wholly owned subsidiary of NBT
immediately prior to the Effective Time (other than Shares held, directly or
indirectly, by NBT, any NBT Subsidiary, BSB or any BSB Subsidiary in trust
accounts, managed accounts and the like or otherwise held in a fiduciary or
custodial capacity that are beneficially owned by third parties and Shares held
by NBT, any NBT Subsidiary, BSB or any BSB Subsidiary in respect of debt
previously contracted) shall be cancelled and extinguished without any
conversion thereof and no payment shall be made with respect thereto.


                                       5
<PAGE>   6

                  SECTION 1.09.  Exchange of Certificates.

                           (a)      Exchange Agent. As of the Effective Time,
NBT shall deposit, or shall cause to be deposited, with American Stock Transfer
& Trust Company (the "Exchange Agent"), solely for the benefit of the holders of
Shares, for exchange in accordance with this Article I through the Exchange
Agent, certificates representing the shares of NBT Common Stock (such
certificates for shares of NBT Common Stock, and cash in lieu of fractional
shares (if any), together with any dividends or distributions with respect
thereto, being hereinafter referred to as the "Exchange Fund", issuable pursuant
to Section 1.08 in exchange for outstanding Shares.

                           (b)      Exchange Procedures. Within two Business
Days after the Effective Time, NBT shall cause the Exchange Agent to mail or
personally deliver to each holder of record (or his or her attorney-in-fact) of
a certificate or certificates which immediately prior to the Effective Time
represented outstanding Shares (the "Certificates"), whose Shares were converted
into the right to receive shares of NBT Common Stock pursuant to Section 1.08
and cash in lieu of fractional shares of NBT Common Stock (if any), (i) a letter
of transmittal (which shall specify that delivery shall be effected, and risk of
loss and title to the Certificates shall pass, only upon delivery of the
Certificates to the Exchange Agent and shall be in such form and have such other
provisions as NBT and BSB may reasonably specify) and (ii) instructions for use
in effecting the surrender of the Certificates in exchange for certificates
representing whole shares of NBT Common Stock together with any dividends or
distributions with respect thereto and any cash in lieu of fractional shares.
Upon surrender of a Certificate for cancellation to the Exchange Agent, together
with such letter of transmittal, duly executed, and such other documentation as
may be required pursuant to such instructions, the holder of such Certificate
shall be entitled to receive in exchange therefor a certificate representing
that number of whole shares of NBT Common Stock, which such holder has the right
to receive in respect of the Shares formerly represented by such Certificate
surrendered pursuant to the provisions of this Article I (after taking into
account all Shares then held by such holder) and cash in lieu of fractional
shares of NBT Common Stock (if any) to which such holder is entitled pursuant to
Section 1.09(e) and any dividends or other distributions to which such holder is
entitled pursuant to Section 2.02(c), and the Certificate so surrendered shall
forthwith be cancelled. In the event of a transfer of ownership of Shares which
is not registered in the transfer records of BSB, a certificate representing the
proper number of shares of NBT Common Stock may be issued to a transferee if the
Certificate representing such Shares is presented to the Exchange Agent,
accompanied by all documents required to evidence and effect such transfer and
by evidence that any applicable stock transfer taxes have been paid. Until
surrendered as contemplated by this Section 1.09, each Certificate shall be
deemed at any time after the Effective Time to represent only the right to
receive upon such surrender the certificate representing shares of NBT Common
Stock, cash in lieu of any fractional shares of NBT Common Stock to which such
holder is entitled pursuant to Section 1.09(e) and any dividends or other
distributions to which such holder is entitled pursuant to Section 1.09(c).

                           (c)      Distributions with Respect to Unexchanged
Shares. No dividends or other distributions declared or made after the Effective
Time with respect to


                                       6
<PAGE>   7

NBT Common Stock with a record date after the Effective Time shall be paid to
the holder of any unsurrendered Certificate with respect to the shares of NBT
Common Stock represented thereby, and no cash payment in lieu of fractional
shares of NBT Common Stock (if any) shall be paid to any such holder pursuant to
Section 1.09(e), until the holder of such Certificate shall surrender such
Certificate. Subject to the effect of applicable laws, following surrender of
any such Certificate, there shall be paid to the holder of the certificates
representing whole shares of NBT Common Stock issued in exchange therefor,
without interest, (i) promptly, the amount of any cash payable with respect to a
fractional share of NBT Common Stock to which such holder is entitled pursuant
to Section 1.09(e) and the amount of dividends or other distributions with a
record date after the Effective Time theretofore paid with respect to such whole
shares of NBT Common Stock, and (ii) at the appropriate payment date, the amount
of dividends or other distributions, with a record date after the Effective Time
but prior to surrender and a payment date occurring after surrender, payable
with respect to such whole shares of NBT Common Stock.

                           (d)      No Further Rights in the Shares. All shares
of NBT Common Stock issued upon conversion of the Shares in accordance with the
terms hereof (including any cash paid pursuant to Section 1.09(e)) shall be
deemed to have been issued in full satisfaction of all rights pertaining to such
Shares. In accordance with Delaware Law, there shall be no appraisal rights
available to holders of BSB Common Stock or NBT Common Stock in connection with
the Merger.

                           (e)      No Fractional Shares. Notwithstanding
anything to the contrary contained herein, no certificates or scrip representing
fractional shares of NBT Common Stock shall be issued upon the surrender for
exchange of Certificates, and such fractional share interest will not entitle
the owner thereof to vote or to any other rights of a stockholder of NBT. Each
holder of a fractional share interest shall be paid an amount in cash equal to
the product obtained by multiplying (i) such fractional share interest to which
such holder (determined after taking into account all fractional share interests
then held by such holder) would otherwise be entitled to receive pursuant to
Section 1.08 hereof multiplied by (ii) the actual market value of NBT Common
Stock, which shall be deemed to be the average of the daily closing prices per
share of NBT Common Stock for the twenty consecutive trading days on which
shares of NBT are actually traded on the Nasdaq National Market ending on the
third trading day preceding the date of the Effective Time as reported by the
Wall Street Journal.

                           (f)      Termination of Exchange Fund. Any portion of
the Exchange Fund which remains undistributed to the stockholders of BSB for
twelve months after the Effective Time shall be delivered to NBT, upon demand,
and any stockholders of BSB who have not theretofore complied with this Article
I shall thereafter look only to NBT for the shares of NBT Common Stock, any cash
in lieu of fractional shares of NBT Common Stock to which they are entitled
pursuant to Section 1.09(e) and any dividends or other distributions with
respect to NBT Common Stock to which they are entitled pursuant to Section
1.09(c). Any portion of the Exchange Fund remaining unclaimed by holders of
Shares as of a date which is immediately prior to such time as such amounts
would otherwise escheat to or become property of any government entity shall, to
the extent permitted by applicable Law, become the property of NBT free and
clear of any claims or interest of any person previously entitled thereto.


                                       7
<PAGE>   8

                           (g)      No Liability. Neither NBT, or BSB shall be
liable to any holder of Shares for any such Shares (or dividends or
distributions with respect thereto) or cash delivered to a public official
pursuant to any abandoned property, escheat or similar Law.

                           (h)      Withholding Rights. NBT shall be entitled to
deduct and withhold from the consideration otherwise payable pursuant to this
Agreement to any holder of Shares such amounts as NBT is required to deduct and
withhold with respect to the making of such payment under the Code, or any
provision of state, local or foreign tax law. To the extent that amounts are so
withheld by NBT, such withheld amounts shall be treated for all purposes of this
Agreement as having been paid to the holder of the Shares in respect of which
such deduction and withholding were made by NBT.

                           (i)      Lost, Stolen or Destroyed Certificates. In
the event any Certificate shall have been lost, stolen or destroyed, upon the
making of an affidavit of that fact by the person claiming such Certificate to
be lost, stolen or destroyed and, if required by NBT, the posting by such person
of a bond in such amount as NBT may reasonably direct as indemnity against any
claim that may be made against it with respect to such Certificate, the NBT will
issue or cause to be issued, in exchange for such lost, stolen or destroyed
Certificate, the number of whole shares of NBT Common Stock and pay or cause to
be paid the amounts deliverable in respect thereof pursuant to Sections 1.09(e)
and 1.09(c) of this Agreement.

                  SECTION 1.10.  Treatment of Stock Options.

                           (a)      At the Effective Time, each option granted
(including any option heretofore assumed) by BSB to purchase Shares which is
outstanding and unexercised immediately prior thereto shall be assumed by NBT.
Such options shall cease to represent a right to acquire Shares and shall be
converted automatically into an option to purchase shares of NBT Common Stock in
an amount and at an exercise price determined as provided below:

                                    (i)     the number of shares of NBT Common
         Stock to be subject to the assumed option shall be equal to the product
         of the number of shares of BSB Common Stock subject to the option
         originally granted by BSB, as previously adjusted, and the Exchange
         Ratio; provided that any fractional shares of NBT Common Stock
         resulting from such multiplication shall be rounded down to the nearest
         whole share; and

                                    (ii)    the exercise price per share of NBT
         Common Stock under the assumed option shall be equal to the exercise
         price per share of BSB Common Stock under the option originally granted
         by BSB, as previously adjusted, divided by the Exchange Ratio, provided
         that such exercise price shall be rounded up to the nearest whole cent.

                           (b)      The assumption of BSB options by NBT, as
provided herein, shall comply with the requirements of Section 424(a) of the
Code. The duration and other terms of the assumed option shall be the same as
the original option except as provided in Sections 1.10(a)(i) and (ii) and
except that all references to BSB shall be deemed to be


                                       8
<PAGE>   9

references to NBT. Nothing herein shall be construed as preventing any option
holder from exercising an option prior to the Effective Time in accordance with
the terms thereof.

                           (c)      At the Effective Time, by virtue of the
Merger and without the need of any further corporate action, NBT shall assume
the BSB 1986 Long-Term Incentive and Capital Accumulation Plan, as amended, the
1996 Long-Term Incentive and Capital Accumulation Plan, as amended, and the
Directors Stock Option Plan (the "BSB Stock Plans"), with the result that all
obligations of BSB under the BSB Stock Plans, including with respect to stock
options issued by BSB that are outstanding at the Effective Time under each BSB
Stock Plan, shall be obligations of NBT following the Effective Time.

                           (d)      No later than 45 days after the Effective
Time, NBT shall prepare and file with the SEC a registration statement on Form
S-8 (or another appropriate form) registering a number of shares of NBT Common
Stock equal to the number of shares subject to the options assumed hereunder.
Such registration statement shall be kept effective (and the current status of
the prospectus or prospectuses required thereby shall be maintained) at least
for so long as any assumed options may remain outstanding.

                           (e)      As soon as practicable after the Effective
Time, NBT shall deliver to the holders of options to purchase BSB Common Stock
appropriate notices setting forth such holders' rights pursuant to BSB Stock
Plans and the agreements pursuant to which such options were issued, and the
agreements evidencing the grant of such options shall be assumed by NBT and
shall continue in effect on the same terms and conditions (subject to the
adjustments required by this Section 1.10 after giving effect to the Merger).

                           (f)      Prior to the Effective Time, NBT and BSB
shall take commercially reasonably steps necessary to cause the transactions
contemplated hereby and any other dispositions of equity securities of BSB
(including derivative securities) or acquisitions of NBT equity securities
(including derivative securities) in connection with this Agreement by each
individual who (a) is a director or officer of NBT or (b) at the Effective Time,
will become a director or officer of NBT, that may qualify for exemption under
Rule 16b-3 promulgated under the Securities Exchange Act of 1934, as amended
(the "Exchange Act") to be exempt thereunder.

                  SECTION 1.11.  Stock Transfer Books.

                  At the Effective Time, the stock transfer books of BSB shall
be closed and there shall be no further registration of transfers of Shares
thereafter on the records of BSB. From and after the Effective Time, the holders
of Certificates shall cease to have any rights with respect to such Shares
except as otherwise provided herein or by any Laws. On or after the Effective
Time, any Certificates presented to the Exchange Agent or NBT for any reason
shall be treated in accordance with this Article I, any cash in lieu of
fractional shares of NBT Common Stock to which the holders thereof are entitled
pursuant to Section 1.09(e) and any dividends or other distributions to which
the holders thereof are entitled pursuant to Section 1.09(c).


                                       9
<PAGE>   10

                  SECTION 1.12.  Anti-Dilution Adjustment.

                  If, subsequent to the date hereof and prior to the Effective
Time, NBT shall pay a stock dividend or make a distribution on NBT Common Stock
or other capital stock of NBT in shares of NBT Common Stock or other capital
stock of NBT or any security convertible into NBT Common Stock or other capital
stock of NBT or shall combine, subdivide, reclassify or recapitalize its stock,
then in each such case, from and after the record date for determining the
stockholders entitled to receive such dividend or distribution of the securities
from such combination or subdivision, an appropriate adjustment shall be made to
the Exchange Ratio, for purposes of determining the number of shares of NBT
Common Stock into which BSB Common Stock shall be converted pursuant to Section
1.8 hereof. For purposes hereof, the payment of a dividend in NBT Common Stock,
or the distribution on NBT Common Stock of securities convertible into NBT
Common Stock, shall be deemed to have effected an increase in the number of
outstanding shares of NBT Common Stock equal to the number of shares of NBT
Common Stock into which such securities shall be initially convertible without
the payment by the holder thereof of any consideration other than the surrender
for cancellation of such convertible securities.

                  SECTION 1.13.  Tax Consequences

                  It is intended that the Merger and Bank Merger shall each
constitute a reorganization within the meaning of Section 368(a) of the Code,
and that this Agreement shall constitute a "plan of reorganization" for purposes
of the Code. In the event that the requirements of such section would not be
satisfied as a result of the Merger or the Bank Merger, NBT and BSB will use
commercially reasonable efforts to restructure the transaction in a manner that
would satisfy such requirements.

                                   ARTICLE II

                      REPRESENTATIONS AND WARRANTIES OF BSB

                  Except as set forth in the disclosure schedule delivered by
BSB to NBT prior to the execution of this Agreement which shall identify
exceptions by specific Section references (provided that disclosure in one
schedule will be deemed to satisfy disclosure in another schedule) (the "BSB
Disclosure Schedule"), BSB hereby represents and warrants to NBT that:

                  SECTION 2.01.  Organization and Qualification of BSB;
                  Subsidiaries.

                           (a)      BSB is a corporation duly organized, validly
existing and in good standing under the laws of the State of Delaware. BSB is
duly registered as a bank holding company with the Board of Governors of the FRB
under the BHCA. BSB has the corporate power and authority to own or lease all of
its properties and assets and to carry on in its business as it is now being
conducted and is duly licensed or qualified to do business in each jurisdiction
in which the nature of any material business conducted by it or the character or
the location of any material properties or assets owned or leased by it makes
such licensing or qualification necessary.


                                       10
<PAGE>   11

                           (b)      BSB Bank is a New York-chartered commercial
bank and trust company duly organized and validly existing and in good standing
under the laws of the State of New York. The deposit accounts of BSB Bank are
insured to the applicable limits by the Federal Deposit Insurance Corporation
("FDIC") through the Bank Insurance Fund ("BIF") to the fullest extent permitted
by law, and all premiums and assessments required in connection therewith have
been paid by BSB Bank. BSB Bank has the corporate power and authority to own or
lease all of its properties and assets and to carry on in its business as it is
now being conducted and is duly licensed or qualified to do business in each
jurisdiction in which the nature of any material business conducted by it or the
character or the location of any material properties or assets owned or leased
by it makes such licensing or qualification necessary.

                           (c)      Section 2.01(c) of the BSB Disclosure
Schedule sets forth a true and complete list of each of BSB's subsidiaries (the
"BSB Subsidiaries") and all outstanding equity securities of each BSB Subsidiary
and the percentage owned by BSB of such equity securities. Each BSB Subsidiary
is wholly owned, directly or indirectly, by BSB. Except as set forth in Section
2.01(c) of the BSB Disclosure Schedule, all outstanding shares of capital stock
of BSB Subsidiaries are validly issued, fully paid and nonassessable and are
free and clear of any lien, claim, charge, option, encumbrance, agreement,
mortgage, pledge, security interest or restriction (each, a "Lien") with respect
thereto. Each BSB Subsidiary is a corporation, partnership, savings bank,
savings and loan, bank or trust company duly incorporated or organized, validly
existing and in good standing under the laws of its jurisdiction of
incorporation or organization.

                           (d)      Each of BSB and each BSB Subsidiary has the
requisite corporate power and authority and is in possession of all franchises,
grants, authorizations, licenses, permits, easements, consents, certificates,
approvals and orders ("BSB Permits") necessary to own, lease and operate its
properties and to carry on its business as is now being conducted, except where
the failure to be so organized, existing and in good standing or to have such
power, authority and BSB Permits would not, either individually or in the
aggregate, have a Material Adverse Effect (as defined in Section 8.04 hereof) on
BSB and the BSB Subsidiaries, taken as a whole. BSB has not received any notice
of proceedings relating to the revocation or modification of any BSB Permits,
except for any such revocation or modification which would not, either
individually or in the aggregate, have a Material Adverse Effect on BSB and the
BSB Subsidiaries, taken as a whole. BSB and each BSB Subsidiary is duly
qualified or licensed as a foreign corporation to do business, and is in good
standing, in each jurisdiction where the character of the properties owned,
leased or operated by it or the nature of its activities makes such
qualification or licensing necessary, except for such failures to be so duly
qualified or licensed and in good standing that would not, either individually
or in the aggregate, have a Material Adverse Effect on BSB and the BSB
Subsidiaries, taken as a whole.

                           (e)      Section 2.01(e) of the BSB Disclosure
Schedule sets forth a true, complete and correct list of all corporations,
partnerships, limited liability companies or other organizations, whether an
incorporated or unincorporated organization (each a "Corporate Entity") of which
BSB or any BSB Subsidiary holds or beneficially owns 5% or more of the
outstanding shares of any class of voting securities, a general partnership
interest or other controlling interest, more than 24.9% of the outstanding
capital stock


                                       11
<PAGE>   12

(whether voting or nonvoting) and subordinated debt or is otherwise deemed to be
a subsidiary within the meaning of the BHCA.

                  SECTION 2.02.  Certificate of Incorporation and Bylaws.

                  BSB and the BSB Subsidiaries have heretofore furnished or made
available to NBT a complete and correct copy of their respective Certificates of
Incorporation and the Bylaws, as amended or restated. Such Certificates of
Incorporation and Bylaws are in full force and effect and none of BSB or the BSB
Subsidiaries are in violation of any of the provisions of their respective
Certificates of Incorporation or Bylaws.

                  SECTION 2.03.  Capitalization.

                           (a)      Capitalization of BSB. The authorized
capital stock of BSB as of March 31, 2000 consists of (i) 30,000,000 Shares, of
which, 10,256,545 shares were issued and outstanding, all of which are validly
issued, fully paid and non-assessable, and all of which have been issued in
compliance with applicable securities laws, and (ii) 2,500,000 shares of serial
preferred stock, par value $.01 per share ("BSB Preferred Stock"), of which no
shares are issued and outstanding. Since January 31, 2000 no shares of BSB
Common Stock have been issued, except for shares issued upon exercise of options
outstanding as of January 31, 2000 under the BSB Stock Plans. As of March 31,
2000, BSB had outstanding 963,730 options issued under the BSB Stock Plans, of
which 619,346 were exercisable. No options have been granted since February 28,
2000 to the date of this Agreement under the BSB Stock Plans. As of the date of
this Agreement, 1,174,216 shares of BSB Common Stock are held as treasury stock
by BSB. Other than pursuant to the BSB Rights Agreement, the BSB Stock Plans and
the BSB Stock Option Agreement, there are no options, warrants or other rights,
rights of first refusal, agreements, arrangements, or commitments of any
character relating to the issued or unissued capital stock of BSB or obligating
BSB to issue or sell any shares of capital stock of, or other equity interests
in, BSB. There are no obligations, contingent or otherwise, of BSB to
repurchase, redeem or otherwise acquire any shares or to provide funds to or
make any investment (in the form of a loan, capital contribution or otherwise)
in any other entity (including any BSB Subsidiary) other than pursuant to the
BSB Rights Agreement.

                           (b)      Capital Stock of the BSB Subsidiaries.
Except as set forth in Section 2.03(b) of the BSB Disclosure Schedule, there are
no options, warrants or other rights, rights of first refusal, agreements,
arrangements or commitments of any character relating to the issued or unissued
capital stock of the BSB Subsidiaries or obligating any BSB Subsidiary to issue
or sell any shares of capital stock of, or other equity interests in any BSB
Subsidiary. There are no obligations, contingent or otherwise, of any BSB
Subsidiary to repurchase, redeem or otherwise acquire any shares of the capital
stock of any BSB Subsidiary or to provide funds to or make any investment (in
the form of a loan, capital contribution or otherwise) in any other entity.

                  SECTION 2.04.  Authority; State Takeover Laws; Certificate of
                  Incorporation.

                           (a)      BSB has the requisite corporate power and
authority to execute and deliver this Agreement, to perform its obligations
hereunder and to


                                       12
<PAGE>   13

consummate the transactions contemplated hereby. The execution and delivery of
this Agreement by BSB and the consummation by BSB of the transactions
contemplated hereby have been duly and validly authorized by all necessary
corporate action on the part of BSB and no other corporate proceedings on the
part of BSB are necessary to authorize this Agreement or to consummate the
transactions contemplated hereby (other than the approval of this Agreement by
the holders of a majority of the outstanding BSB Common Stock entitled to vote
thereon in accordance with Delaware Law and BSB's Certificate of Incorporation
and Bylaws). This Agreement has been duly and validly executed and delivered by
BSB and, assuming the due authorization, execution and delivery by NBT,
constitutes the legal, valid and binding obligation of BSB enforceable in
accordance with its terms, except as enforcement may be limited by bankruptcy,
insolvency and similar laws affecting creditors' rights and remedies generally
and by general principles of equity.

                           (b)      The Board of Directors of BSB has taken all
actions necessary under Delaware Law and BSB's Certificate of Incorporation,
including approving the transactions contemplated herein, to insure that the
restrictions on business combinations set forth in Delaware Law do not or will
not apply to this Agreement, the transactions contemplated herein, the BSB Stock
Option Agreement or the transactions contemplated therein or any transaction
between NBT or its affiliates, on the one hand, and BSB or its affiliates, on
the other hand, following the exercise of the option granted under the BSB Stock
Option Agreement.

                  SECTION 2.05.  No Conflict; Required Filings and Consents.

                           (a)      Except as set forth in Section 2.05(a) of
the BSB Disclosure Schedule, the execution and delivery of this Agreement by BSB
does not, and the performance of this Agreement by BSB shall not, (i) conflict
with or violate the Certificate of Incorporation or Bylaws of BSB or any BSB
Subsidiary, (ii) conflict with or violate any domestic (federal, state or local)
or foreign law, statute, ordinance, rule, regulation, order, judgment, decision,
writ, injunction or decree (collectively, "Laws") applicable to BSB or any BSB
Subsidiary, or by which its respective properties are bound or affected, or
(iii) result in any breach of or constitute a default (or an event that with
notice or lapse of time or both would become a default) under, or give to others
any rights of termination, amendment, acceleration or cancellation of, or result
in the creation of a Lien on any of the properties or assets of BSB or any BSB
Subsidiary pursuant to any note, bond, mortgage, indenture, contract, agreement,
lease, license, permit, franchise or other instrument or obligation to which BSB
or any BSB Subsidiary is a party or by which BSB or any BSB Subsidiary or its
respective properties are bound or affected, except (in the case of clauses (ii)
and (iii) of this Section 2.05(a)) for any such conflicts, violations, breaches,
defaults or other occurrences that would not, either individually or in the
aggregate, have a Material Adverse Effect on BSB and the BSB Subsidiaries, taken
as a whole.

                           (b)      The execution and delivery of this Agreement
by BSB does not, and the performance of this Agreement by BSB shall not, require
any consent, approval, authorization or permit of, or filing with or
notification to, any governmental or regulatory authority, domestic or foreign,
("Approvals") except (i) the filing of applications, notices and waiver
requests, as applicable, as to the Merger and the Bank Merger with the FRB under
the BHCA and the Office of the Comptroller of the Currency ("OCC") under the
National


                                       13
<PAGE>   14

Bank Act, 12 USC section 1 et seq. ("National Bank Act") and the Bank Merger
Act, 12 USC 1828(c) (the "Bank Merger Act"), and the approval of the foregoing
applications, notices and waiver requests; (ii) the filing of any required
applications or notices with the OCC as to the subsidiary activities of BSB
Bank, and the approval of the foregoing applications and notices; (iii) courtesy
notice of the Bank Merger to the New York State Banking Department (the "NYSBD")
and, if deemed necessary by the NYSBD, the filing of an application with the
NYSBD for NBT to become a bank holding company under New York law for a moment
in time and the approval of such application; (iv) the filing with the SEC of a
registration statement on Form S-4 to register the shares of NBT Common Stock to
be issued in connection with the Merger (including the shares of NBT Common
Stock that may be issued upon the exercise of the options referred to in Section
1.10 hereof), which will include the joint proxy statement/prospectus to be used
in soliciting the approval of BSB and NBT stockholders at special meetings to be
held in connection with this Agreement and the transactions contemplated hereby
(such joint proxy statement as amended or supplemented is referred to herein as
the "Joint Proxy Statement"), (v) the approval of this Agreement by the
requisite vote of the stockholders of BSB, (vi) the approval by NBT stockholders
of (A) this Agreement and the issuance of NBT Common Stock in the Merger
pursuant to this Agreement and (B) the amendments to NBT's Certificate of
Incorporation to increase the number of shares of NBT Common Stock that NBT is
authorized to issue and to provide a new name for the Surviving Corporation;
(vii) the filing of the Certificate of Merger with the Secretary of State of
Delaware pursuant to the Delaware Law, (viii) the filings required by the
National Bank Act and OCC regulations, (ix) the filings required by NASDAQ to
list additional shares; (x) such consents, approvals, orders, authorizations,
registrations, declarations and filings as may be required under applicable
federal, foreign and state securities (or related) laws and, if applicable, the
Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (the "HSR
Act"), and the securities or antitrust laws of any foreign country, and (xi)
such filings, authorizations or approvals as may be set forth in Section 2.05(b)
of the BSB Disclosure Schedule. No consents or approvals of or filings or
registrations with any court, administrative agency or commission or other
governmental authority or instrumentality (each a "Governmental Entity"), or
with any third party are necessary in connection with (1) the execution and
delivery by BSB of this Agreement and the BSB Stock Option Agreement, (2) the
consummation by BSB of the Merger and the other transactions contemplated
hereby, (3) the execution and delivery by BSB Bank of the Bank Merger Agreement,
(4) the performance by BSB of its obligations under the BSB Stock Option
Agreement; and (5) the consummation by BSB Bank of the Bank Merger and the
transactions contemplated thereby, except, in each case, for such consents,
approvals or filings, the failure of which to obtain will not have a Material
Adverse Effect on the ability of BSB to consummate the transactions contemplated
hereby.

                           (c)      BSB hereby represents to NBT that it has no
knowledge of any reason why approval or effectiveness of any of the
applications, notices or filings referred to in Section 2.05 cannot be obtained
or granted on a timely basis.

                  SECTION 2.06.  Compliance.

                  Neither BSB nor any BSB Subsidiary is in conflict with, or in
default or violation of (i) any Law applicable to BSB or the BSB Subsidiaries or
by which any of their respective properties are bound or affected, or (ii) any
note, bond, mortgage, indenture,


                                       14
<PAGE>   15

contract, agreement, lease, license, permit, franchise or other instrument or
obligation to which BSB or any BSB Subsidiary is a party or by which BSB or any
BSB Subsidiary or any of their respective properties are bound or affected,
except for any such conflicts, defaults or violations which would not, either
individually or in the aggregate, have a Material Adverse Effect on BSB and the
BSB Subsidiaries, taken as a whole.

                  SECTION 2.07.  Securities and Banking Reports; Financial
                  Statements.

                           (a)      BSB and the BSB Subsidiaries have filed,
except as set for in Schedule 2.07 of the BSB Disclosure Schedule, all material
forms, reports, registrations, statements and documents, together with any
amendments required to be made with respect thereto that were required to be
filed since January 1, 1995 with (i) the SEC and (ii)(A) any self regulatory
organization ("SRO"), (B) any other federal, state or foreign governmental or
regulatory agency or authority (collectively with the SEC and the SROs,
"Regulatory Agencies") and (C) all other reports and statements (the filings
made with the entities listed in subclause (ii) (being referred to as "Other
Reports") required to be filed by BSB and any BSB Subsidiary since January 1,
1995, and paid all fees and assessments due and payable in connection therewith,
except, in the case of the Other Reports, where failure to file such form,
report, registration, statement or document or pay such fees and assessments
would not, either individually or in the aggregate, have a Material Adverse
Effect on BSB and the BSB Subsidiaries, taken as a whole (all such forms,
reports, registrations, statements and documents are collectively referred to as
the "BSB Reports"). The BSB Reports, including all BSB Reports filed after the
date of this Agreement, (i) were, or will be, prepared in accordance with the
requirements of applicable Law and (ii) did not at the time they were filed, or
will not at the time they are filed, contain any untrue statement of material
fact or omit to state a material fact required to be stated therein or necessary
in order to make the statements therein, in the light of circumstances under
which they were made, not misleading.

                           (b)      Each of the consolidated financial
statements (including, in each case, any related notes thereto) contained in any
filings with the SEC since January 1, 1995 (the "BSB SEC Reports"), including
any BSB SEC Reports filed since the date of this Agreement and prior to or at
the Effective Time, have been, or will be, prepared in accordance with generally
accepted accounting principles applied on a consistent basis ("GAAP") throughout
the periods involved (except as may be indicated in the notes thereto) and each
fairly presents, or will fairly present, in all material respects, the
consolidated financial position of BSB and the BSB Subsidiaries as of the
respective dates thereof and the consolidated results of its operations and
changes in financial position for the periods indicated, except that any
unaudited interim financial statements were or are subject to normal and
recurring year-end adjustments which were not or are not expected to be material
in amount.

                           (c)      Except as and to the extent set forth on the
consolidated balance sheet of BSB and the BSB Subsidiaries as of December 31,
1999, including all notes thereto (the "BSB Balance Sheet"), neither BSB nor any
BSB Subsidiary has any liabilities or obligations of any nature (whether
accrued, absolute, contingent or otherwise), except for (i) liabilities or
obligations incurred in the ordinary course of business since December 31, 1999
and (ii) liabilities or obligations that would not, either individually or in


                                       15
<PAGE>   16

the aggregate, have a Material Adverse Effect on BSB and the BSB Subsidiaries,
taken as a whole.

                  SECTION 2.08.  Absence of Certain Changes or Events.

                           Except as disclosed in the BSB SEC Reports filed
prior to the date of this Agreement, since December 31, 1999, (a) BSB and the
BSB Subsidiaries have conducted their businesses only in the ordinary course and
in a manner consistent with past practice and (b) there has been no event which
has had, or is reasonably likely to result in, either individually or in the
aggregate, a Material Adverse Effect on BSB and the BSB Subsidiaries, taken as a
whole.

                  SECTION 2.09.  Absence of Litigation and Agreements.

                           (a)      Except as disclosed in the BSB SEC Reports
filed prior to the date of this Agreement or set forth in Section 2.09 of the
BSB Disclosure Schedule, (i) neither BSB nor any BSB Subsidiary is subject to
any continuing order of, or written agreement or memorandum of understanding
with, or continuing investigation by, any federal or state savings and loan or
bank regulatory authority or other governmental entity or regulatory authority,
or any judgment, order, writ, injunction, decree or award of any governmental
entity or regulatory authority or arbitrator, including, without limitation,
cease-and-desist or other orders which, either individually or in the aggregate,
would have or reasonably be expected to have a Material Adverse Effect on BSB
and the BSB Subsidiaries, taken as a whole; (ii) there is no claim of any kind,
action, suit, litigation, proceeding, arbitration, investigation, or controversy
affecting BSB or the BSB Subsidiaries pending or, to the knowledge of BSB,
threatened, except (A) as of the date of this Agreement, for matters which
individually seek damages not in excess of $500,000 and (B) as of the Closing
(as defined in Section 8.01), for matters which otherwise cannot reasonably be
expected to have, either individually or in the aggregate, a Material Adverse
Effect on BSB and the BSB Subsidiaries, taken as a whole; and (iii) there are
not uncured violations, or violations with respect to which refunds or
restitutions may be required, cited in any compliance report to BSB or the BSB
Subsidiaries as a result of the examination by any bank regulatory authority,
which would have or reasonably be expected to have, either individually or in
the aggregate, a Material Adverse Effect on BSB and the BSB Subsidiaries, taken
as a whole.

                           (b)      Except as set forth on the BSB Disclosure
Schedule at Section 2.09, neither BSB nor any of the BSB Subsidiaries is a party
to any written agreement or memorandum of understanding with, or party to any
commitment letter, board resolution submitted to a regulatory authority or
similar undertaking to, or is subject to any order or directive by, or is a
recipient of any extraordinary supervisory letter from any governmental entity
or agency which restricts materially the conduct of its business, or in any
manner relates to its capital adequacy, its credit or reserve policies or its
management nor has BSB or any BSB Subsidiary (i) been advised by any
governmental entity or agency that it is contemplating issuing or requesting (or
is considering the appropriateness of issuing or requesting) any such order,
decree, agreement, memorandum of understanding, extraordinary supervisory
letter, commitment letter or similar submission or (ii) have knowledge of any
pending or threatened regulatory investigation.


                                       16
<PAGE>   17

Neither BSB nor any BSB Subsidiary is required by Section 32 of the Federal
Deposit Insurance Act to give prior notice to a Federal banking agency of the
proposed addition of an individual to its board of directors or the employment
of an individual as a senior executive officer.

                  SECTION 2.10.  Employee Benefit Plans.

                  (a)      Section 2.10 of the BSB Disclosure Schedule sets
forth a true and complete list of all benefit plans, arrangements, commitments
and payroll practices (whether or not employee benefit plans ("BSB Plans" or
"BSB Plan") as defined in Section 3(3) of the Employee Retirement Income
Security Act of 1974, as amended ("ERISA"), including, without limitation, sick
leave, vacation pay, severance pay, salary continuation for disability,
consulting or other compensation arrangements, retirement, deferred
compensation, bonus, incentive compensation, stock purchase, stock option,
health, including hospitalization, medical and dental, life insurance and
scholarship programs maintained as of the date of this Agreement or within the
last six years of the date of this Agreement, for the benefit of any present or
former employees of BSB, any of the BSB Subsidiaries or any other entity which
together with BSB would be deemed a "single employer" within the meaning of
Section 4001 of ERISA or Code Sections 414(b), (c), (m) or (o) ("BSB ERISA
Affiliate") or to which BSB or any BSB ERISA Affiliate has contributed or is or
was within the last six years obligated to make payments.

                  (b)      With respect to each BSB Plan, BSB has heretofore
delivered or made available to NBT true, correct and complete copies of the plan
document, trust agreement, if any, all insurance policies, if any, and all
material related documents, including, but not limited to, (i) the actuarial
report for each BSB Plan that is a defined benefit plan, funded welfare plan or
other plan requiring actuarial valuation for each of the last five years, (ii)
the most recent determination letter from the Internal Revenue Service ("IRS"),
if such BSB Plan is intended to be a qualified plan under Section 401(a) of the
Code, (iii) the current summary plan description and each summary of material
modification, (iv) each Form 5500 series filed for the preceding five plan
years, (v) each agreement with each fiduciary and service provider relating to
such BSB Plan, and (vi) all substantive correspondence relating to such BSB Plan
addressed to or received from the IRS, the U.S. Department of Labor ("DOL"), the
Pension Benefit Guaranty Corporation ("PBGC") or any other governmental agency;
(vii) each bond required by Section 412 of ERISA, each fiduciary liability
insurance policy, and each agreement to indemnify any fiduciary, including each
amendment to any such document.

                  (c)      Except as set forth in Section 2.10(c) of the BSB
Disclosure Schedule:

                           (i)      Each BSB Plan has been operated and
administered in all material respects in compliance with the terms of its
governing document(s) and instrument(s) and applicable Laws, including, but not
limited to, ERISA and the Code, and the funding, filing, termination, reporting
and disclosure and continuation coverage obligations pursuant to Title V of the
Consolidated Omnibus Budget Reconciliation Act of 1985, as amended ("COBRA");

                           (ii)     Each BSB Plan that is intended to be
"qualified" within the meaning of Section 401(a) of the Code is and from its
inception has been so qualified, and


                                       17
<PAGE>   18

any trust created pursuant to any such Plan is exempt from federal income tax
under Section 501(a) of the Code, each such Plan has received from the Internal
Revenue Service a favorable determination letter to such effect upon which BSB
or a BSB ERISA Affiliate is entitled to rely as to such matters and which is
currently applicable, and neither BSB nor any BSB ERISA Affiliate is aware of
any circumstance or event which would jeopardize the tax-qualified status of any
BSB Plan or the tax-exempt status of any related trust, or which would cause the
imposition of any liability, penalty or tax under ERISA or the Code with respect
to any BSB Plan;

                           (iii)    With respect to each BSB Plan that is
subject to Title IV of ERISA, the present value of accrued benefits under such
BSB Plan, based upon the actuarial assumptions used by the PBGC to determine the
level of funding required in the event of termination of such Plan, did not, as
of its latest valuation date, exceed the then current value of the assets of
such Plan allocable to such accrued benefits;

                           (iv)     No BSB Plan provides benefits, including,
without limitation, death or medical benefits (whether or not insured), with
respect to current or former employees of BSB or any BSB ERISA Affiliate beyond
their retirement or other termination of employment with BSB or a BSB ERISA
Affiliate, other than coverage mandated by applicable Law, death benefits or
retirement benefits under a Plan that is an "employee pension plan," as defined
by Section 3(2) of ERISA, deferred compensation benefits under a BSB Plan that
are accrued as liabilities on the books of BSB or any BSB ERISA Affiliate, or
benefits the full cost of which is borne by the current or former employee (or
his beneficiary);

                           (v)      No liability under Title IV of ERISA has
been incurred by BSB or any BSB ERISA Affiliate that has not been satisfied in
full as of the date of this Agreement, and no condition exists that presents a
material risk of BSB or any BSB ERISA Affiliate incurring a material liability
thereunder;

                           (vi)     No BSB Plan is a "multiemployer plan," as
such term is defined in Section 3(37) of ERISA, nor has BSB or any BSB ERISA
Affiliate ever had any obligation to contribute to a multiemployer plan or
otherwise incurred or assumed any liability for complete or partial withdrawal
from such a plan that is a pension plan subject to Title IV of ERISA;

                           (vii)    All contributions or other amounts payable
by BSB or any BSB ERISA Affiliate as of the Effective Time with respect to each
BSB Plan and all other liabilities of each such entity with respect to each such
BSB Plan, with respect to current or prior plan years, have been paid or accrued
in accordance with GAAP and Section 412 of the Code;

                           (viii)   Neither BSB nor any BSB ERISA Affiliate nor
any BSB Plan has engaged in any transaction with respect to which any of the
aforementioned entities could be subject to either a civil liability or civil
penalty assessed pursuant to Sections 409, 501(i) or 502(l) of ERISA or a tax
imposed pursuant to Section 4975 or 4976 of the Code;

                           (ix)     There are and, for the past three years
there have been, no inquiries, proceedings, claims, suits pending or, to the
knowledge of BSB, threatened (other


                                       18
<PAGE>   19

than routine claims for benefits) by any governmental agency or authority or by
any participant or beneficiary against any of the BSB Plans, the assets of any
of the trusts under such Plans or the Plan sponsor or the Plan administrator, or
against any fiduciary of any of such BSB Plans with respect to the design or
operation of a BSB Plan;

                           (x)      Each BSB Plan could be terminated as of the
Effective Time without material liability to BSB or any BSB ERISA Affiliate in
excess of the amount accrued with respect to such Plan on the financial
statements of BSB or such BSB ERISA Affiliate;

                           (xi)     No BSB Plan, either individually or
collectively, provides for any payment by BSB or any BSB ERISA Affiliate that
would not be deductible under Code Sections 162(a)(1), 162(m) or 404, or that
would, after giving effect to the transactions contemplated by this Agreement,
constitute an "excess parachute payment" within the meaning of Code Section
280G, nor would the transactions contemplated by this Agreement accelerate the
time of payment or vesting, or increase the amount of compensation due to any
employee;

                           (xii)    No "accumulated funding deficiency" as
defined in Section 302(a)(2) of ERISA or Section 412 of the Code, whether or not
waived, and no "unfunded current liability" as determined under Section 412(l)
of the Code exists with respect to any BSB Plan subject to Section 412 of the
Code and Section 302 of ERISA, and there are no unsatisfied liabilities to
participants, the IRS, the DOL, or the PBGC as a result of the termination of
any BSB Plan other than any such liabilities that have not become due or that
are being contested in good faith;

                           (xiii)   No BSB Plan has experienced a "reportable
event" (as such term is defined in Section 4043(b) of ERISA) that is not subject
to an administrative or statutory waiver from the reporting requirement;

                           (xiv)    All reports and information required to be
filed with the DOL, IRS and PBGC or with plan participants and their
beneficiaries with respect to each BSB Plan have been filed, and all annual
reports (including Form 5500 series) of such Plans were certified without
qualification by each Plan's accountants and actuaries. Any annual reports which
are not yet due but are required to be filed with respect to a plan year which
ended on or prior to the Effective Date and any annual reports which are
required to be filed with respect to current plan years shall be filed on a
timely basis.

                           (xv)     Any bond required under ERISA with respect
to any BSB Plan has been obtained and is in full force and effect and no funds
held by or under the control of BSB are plan assets of any BSB Plan.

                  SECTION 2.11.  Material Contracts.

                  Except as set forth in Section 2.11 of the BSB Disclosure
Schedule, as of the date of this Agreement, neither BSB nor any BSB Subsidiary
is a party to or bound by (a) any contract or commitment for capital
expenditures in excess of $500,000 for any one project, (b) contracts or
commitments for the purchase of materials or supplies or for the performance of
services over a period of more than 60 days from the date of this Agreement


                                       19
<PAGE>   20

and calling for aggregate future payments of $1,000,000 or more during the term
of such contract or commitment, (c) any contract which is a "material contract"
(as such term is defined in Item 601(b)(10) of Regulation S-K of the SEC) that
has not been filed or incorporated by reference in the BSB SEC Reports, (d) any
contract which contains non-compete or exclusivity provisions or restrictions
with respect to any business or geographic area or (e) any contract which would
prohibit or materially delay the consummation of the Merger or any other
transaction contemplated by this Agreement. Each contract, arrangement,
commitment or understanding of the type described in this Section 2.11, whether
or not set forth in Section 2.11 of the BSB Disclosure Schedule, is referred to
herein as a "BSB Contract". Neither BSB nor any BSB Subsidiary knows of, or has
received notice of, any violation of any BSB Contract by any of the other
parties thereto, except for violations which, individually or in the aggregate,
would not result in a Material Adverse Effect on BSB and the BSB Subsidiaries,
taken as a whole.

                  SECTION 2.12.  Environmental Matters.

                           (a)      Each of BSB and the BSB Subsidiaries is in
compliance in all material respects with all applicable federal and state laws
and regulations relating to pollution or protection of the environment
(including without limitation, laws and regulations relating to emissions,
discharges, releases and threatened releases of Hazardous Materials (as
hereinafter defined), or otherwise relating to the manufacture, processing,
distribution, use, treatment, storage, disposal, transport or handling of
Hazardous Materials.

                           (b)      There is no suit, claim, action, proceeding,
investigation or notice pending or, to the knowledge of BSB, threatened (or, to
the knowledge of BSB, past or present actions or events that could form the
basis of any such suit, claim, action, proceeding, investigation or notice), in
which BSB or any BSB Subsidiary has been or, with respect to threatened suits,
claims, actions, proceedings, investigations or notices may be, named as a
defendant (i) for alleged material noncompliance (including by any predecessor),
with any environmental law, rule or regulation or (ii) relating to any material
release or threatened release into the environment of any Hazardous Material,
occurring at or on a site owned, leased or operated by BSB or any BSB
Subsidiary, or to the knowledge of BSB, relating to any material release or
threatened release into the environment of any Hazardous Material, occurring at
or on a site not owned, leased or operated by BSB or any BSB Subsidiary.

                           (c)      During the period of BSB's or any BSB
Subsidiary's ownership or operation of any of its properties, there has not been
to BSB's knowledge any material release of Hazardous Materials in, on, under or
affecting any such property.

                           (d)      To the knowledge of BSB, neither BSB nor any
BSB Subsidiary has made or participated in any loan to any person who is subject
to any suit, claim, action, proceeding, investigation or notice, pending or
threatened, with respect to (i) any alleged material noncompliance as to any
property securing such loan with any environmental law, rule or regulation, or
(ii) the release or the threatened release into the environment of any Hazardous
Material at a site owned, leased or operated by such person on any property
securing such loan.


                                       20
<PAGE>   21

                           (e)      For purposes of this Agreement, the term
"Hazardous Material" means any hazardous waste, petroleum product,
polychlorinated biphenyl, chemical, pollutant, contaminant, pesticide,
radioactive substance, or other toxic material, or other material or substance
(in each such case, other than small quantities of such substances in retail
containers) regulated under any applicable environmental or public health
statute, law, ordinance, rule or regulation.

                  SECTION 2.13.  Taxes.

                           (a)      Each of BSB and the BSB Subsidiaries has
duly filed all Tax Returns required to be filed by it on or prior to the date
hereof (all such returns being accurate and complete in all material respects)
and has duly paid or made provision on the financial statements referred to in
Sections 2.07 and 5.14 hereof in accordance with GAAP for the payment of all
material Taxes which have been incurred or are due or claimed to be due from it
by Taxing Authorities on or prior to the date hereof other than Taxes (a) which
(x) are not yet delinquent or (y) are being contested in good faith and set
forth in Section 2.13(a) of the BSB Disclosure Schedule and (b) which have not
been finally determined. All liability with respect to the Tax Returns of BSB
and the BSB Subsidiaries has been satisfied for all years to and including 1998.
The IRS has not notified BSB of, or otherwise asserted, that there are any
material deficiencies with respect to the federal income Tax Returns of BSB
subsequent to tax year 1995. Except as set forth in Section 2.13 of the BSB
Disclosure Schedule, there are no material disputes pending, or claims asserted
for Taxes or assessments upon BSB or any BSB Subsidiary, nor has BSB or any BSB
Subsidiary been requested to give any currently effective waivers extending the
statutory period of limitation applicable to any federal or state income Tax
Return for any period. In addition, Tax Returns which are accurate and complete
in all material respects have been filed by BSB and the BSB Subsidiaries for all
periods for which returns were due with respect to income tax withholding,
Social Security and unemployment taxes and the amounts shown on such Tax Returns
to be due and payable have been paid in full or adequate provision therefor in
accordance with GAAP has been included by BSB in the financial statements
referred to in Sections 2.07 hereof and 5.14 hereof. All BSB Tax Returns
relating to federal income taxes have been examined by the relevant Taxing
Authorities, or closed without audit by applicable statutes of limitations, and
all deficiencies proposed as a result of such examinations have been paid or
settled, for all periods before and including the taxable year ended 1995.
Except as set forth in Section 2.13 of the BSB Disclosure Schedule, neither BSB
nor any BSB Subsidiary has consented to any waiver or extension of any statute
of limitations with respect to any Tax. Neither BSB nor any BSB Subsidiary has
made an election under Section 341(f) of the Code. BSB has provided or made
available to NBT complete and correct copies of its Tax Returns and all material
correspondence and documents, if any, relating directly or indirectly to taxes
for each taxable year or other relevant period as to which the applicable
statute of limitations has not run on the date hereof. For this purpose,
"correspondence and documents" include, without limitation, amended Tax Returns,
claims for refunds, notices from Taxing Authorities of proposed changes or
adjustments to Taxes or Tax Returns, consents to assessment or collection of
Taxes, acceptances of proposed adjustments, closing agreements, rulings and
determination letters and requests therefor, and all other written
communications to or from Taxing Authorities relating to any material Tax
liability of BSB or any BSB Subsidiary. BSB will not be a "foreign person" as
that term is used in Section 1.1445-


                                       21
<PAGE>   22

2 of the Treasury Regulations promulgated under the Code. BSB Bank is not a
"United States real property holding corporation" within meaning of Section 897
of the Code and was not a "United States real property holding corporation" on
any "determination date" (as defined in Section 1.897-2(c) of such Regulations)
that occurred during any relevant period.

                           (b)      For purposes of this Agreement:

                  "Tax" means any tax (including any income tax, capital gains
tax, value-added tax, sales tax, property tax, gift tax, or estate tax), levy,
assessment, tariff, duty (including any customs duty), deficiency, or other fee,
and any related charge or amount (including any fine, penalty, interest, or
addition to tax), imposed, assessed, or collected by or under the authority of
any Taxing Authority or payable pursuant to any tax-sharing agreement or any
other contract relating to the sharing or payment of any such tax, levy,
assessment, tariff, duty, deficiency, or fee.

                  "Tax Return" means any return (including any information
return), report, statement, schedule, notice, form, or other document or
information filed with or submitted to, or required to be filed with or
submitted to, any Taxing Authority in connection with the determination,
assessment, collection, or payment of any Tax or in connection with the
administration, implementation, or enforcement of or compliance with any law,
regulation or other legal requirement relating to any Tax.

                  "Taxing Authority" means  any:

                                    (i)     nation, state, county, city, town,
         village, district, or other jurisdiction of any nature;

                                    (ii)    federal, state, local, municipal,
         foreign, or other government;

                                    (iii)   governmental or quasi-governmental
         authority of any nature (including any governmental agency, branch,
         department, official, or entity and any court or other tribunal);

                                    (iv)    multi-national organization or body;
         or

                                    (v)     body exercising, or entitled to
         exercise, any administrative, executive, judicial, legislative, police,
         regulatory, or taxing authority or power of any nature.


                                       22
<PAGE>   23

                  SECTION 2.14.  Affiliates.

                  Each director, executive officer and other person who is an
"affiliate" (for purposes of Rule 145 under the Securities Act of 1933, as
amended (the "Securities Act"), and for purposes of qualifying the Merger for
"pooling-of-interests" accounting treatment) of BSB is listed at Section 2.14 of
the BSB Disclosure Schedule, and except as indicated thereon, each such person
has delivered to NBT concurrently with the execution of this Agreement, a
stockholder agreement in the form of Exhibit F hereto (the "BSB Stockholder
Agreement").

                  SECTION 2.15.  Derivative Instruments.

                  All swap, forward, future, option, cap, floor or collar
financial contracts, and any other interest rate protection contracts
("Derivative Instruments") to which BSB or any BSB Subsidiary is a party or to
which any of their properties or assets may be subject were entered into in the
ordinary course of business and, to the knowledge of BSB, in accordance with
prudent banking practice and applicable rules, regulations, and policies of the
regulatory agencies and with counterparties believed to be financially
responsible at the time and, to the knowledge of BSB, are legal, valid, and
binding obligations enforceable in accordance with their terms (except as may be
limited by bankruptcy, insolvency, moratorium, reorganization, or similar laws
affecting the rights of creditors generally, and the availability of equitable
remedies), and, to the knowledge of BSB, are in full force and effect. BSB and
each BSB Subsidiary has duly performed in all material respects all of its
obligations under any such Derivative Instruments, and to the knowledge of BSB,
there are no breaches, violations, or defaults or allegations or assertions of
such by any party thereunder except for any such breaches, violations, or
defaults or allegations or assertions which would not, individually or in the
aggregate, have a Material Adverse Effect on BSB and the BSB Subsidiaries, taken
as a whole.

                  SECTION 2.16.  Regulatory Approvals.

                  BSB is not aware of any aspect of, or issues relating to, its
or the BSB Subsidiaries' operations and business that would prevent the
condition of Closing set forth in Section 6.01(c) from being satisfied.

                  SECTION 2.17.  Brokers.

                  Except as contemplated by or referenced in the March 17, 2000
letter agreement between Keefe, Bruyette & Woods, Inc. ("KBW") and BSB, a true
and complete copy of which BSB has delivered to NBT, no broker, finder or
investment banker is entitled to any brokerage, finder's or other fee or
commission in connection with the transactions contemplated by this Agreement
based upon arrangements made by or on behalf of BSB or any BSB Subsidiary.

                  SECTION 2.18.  Pooling of Interests and Tax Matters.

                  Neither BSB nor, to the knowledge of BSB, any of its
affiliates (as defined in Section 2.14) has through the date of this Agreement
taken or agreed to take any action that would prevent NBT from accounting for
the business combination to be effected by the


                                       23
<PAGE>   24

Merger and the Bank Merger as a pooling of interests in accordance with GAAP or
would prevent the Merger from qualifying as a reorganization under Section
368(a) of the Code. BSB has no reason to believe that the Merger will not
qualify as a pooling of interests or as a reorganization under Section 368(a) of
the Code.

                  SECTION 2.19.  Vote Required.

                  The requisite affirmative vote of the holders of a majority of
the outstanding BSB Common Stock entitled to vote with respect to the approval
of this Agreement is the only vote of the holders of any class or series of
BSB's capital stock required in connection with the Merger.

                  SECTION 2.20.  Fairness Opinion.

                  BSB has received an opinion from KBW on or prior to the date
of this Agreement to the effect that, as of the date of such opinion, the
Exchange Ratio is fair to the stockholders of BSB, from a financial point of
view ("BSB Fairness Opinion") and KBW has consented to the inclusion of the BSB
Fairness Opinion in the Registration Statement.

                  SECTION 2.21.  Rights Agreement

                  The Board of Directors of BSB has taken such action as is
necessary to render the Series A junior participating preferred stock purchase
rights of BSB under the BSB Rights Agreement inapplicable to the Merger and the
other transactions contemplated by this Agreement.

                                   ARTICLE III

                      REPRESENTATIONS AND WARRANTIES OF NBT

                  Except as set forth in the disclosure schedule delivered by
NBT to BSB prior to the execution of this Agreement (the "NBT Disclosure
Schedule") which shall identify exceptions by specific Section references
(provided that disclosure in one schedule will be deemed to satisfy disclosure
in another schedule), NBT hereby represents and warrants to BSB that:

                  SECTION 3.01.  Organization and Qualification of NBT;
                  Subsidiaries.

                           (a)      NBT is a corporation duly organized, validly
existing and in good standing under the laws of the State of Delaware. NBT is
duly registered as a bank holding company with the Board of Governors of the FRB
under the BHCA. NBT has the corporate power and authority to own or lease all of
its properties and assets and to carry on in its business as it is now being
conducted and is duly licensed or qualified to do business in each jurisdiction
in which the nature of any material business conducted by it or the character or
the location of any material properties or assets owned or leased by it makes
such licensing or qualification necessary.


                                       24
<PAGE>   25

                           (b)      NBT Bank is a national association organized
and validly existing and in good standing under the laws of the United States.
The deposit accounts of NBT Bank are insured by the FDIC through the BIF to the
fullest extent permitted by law, and all premiums and assessments required in
connection therewith have been paid by NBT Bank. NBT Bank has the corporate
power and authority to own or lease all of its properties and assets and to
carry on in its business as it is now being conducted and is duly licensed or
qualified to do business in each jurisdiction in which the nature of any
material business conducted by it or the character or the location of any
material properties or assets owned or leased by it makes such licensing or
qualification necessary.

                           (c)      Section 3.01(c) of the NBT Disclosure
Schedule sets forth a true and complete list of each of NBT's subsidiaries (the
"NBT Subsidiaries"), all outstanding equity securities of each NBT Subsidiary
and the percentages owned by NBT of such equity securities. Except as set forth
in Section 3.01(c) of the NBT Disclosure Schedule, each NBT Subsidiary is wholly
owned, directly or indirectly, by NBT. Except as set forth in Section 3.01(c) of
the NBT Disclosure Schedule, all outstanding shares of capital stock of the NBT
Subsidiaries are validly issued, fully paid and nonassessable and are free and
clear of any Lien, with respect thereto. Each NBT Subsidiary is a corporation,
partnership, savings bank, savings and loan, bank or trust company duly
incorporated or organized validly existing and in good standing under the laws
of its jurisdiction of incorporation or organization.

                           (d)      Each of NBT and each NBT Subsidiary has the
requisite corporate power and authority and is in possession of all franchises,
grants, authorizations, licenses, permits, easements, consents, certificates,
approvals and orders ("NBT Permits") necessary to own, lease and operate its
properties and to carry on its business as it is now being conducted, except
where the failure to be so organized, existing and in good standing or to have
such power, authority and NBT Permits would not, either individually or in the
aggregate, have a Material Adverse Effect on NBT and the NBT Subsidiaries, taken
as a whole. NBT has not received any notice of proceedings relating to the
revocation or modification of any NBT Permits, except for any such revocation or
modification which would not, either individually or in the aggregate, have a
Material Adverse Effect on NBT and the NBT Subsidiaries, taken as a whole. NBT
and each NBT Subsidiary is duly qualified or licensed as a foreign corporation
to do business, and is in good standing, in each jurisdiction where the
character of the properties owned, leased or operated by it or the nature of its
activities makes such qualification or licensing necessary, except for such
failures to be so duly qualified or licensed and in good standing that would
not, either individually or in the aggregate, have a Material Adverse Effect on
NBT and the NBT Subsidiaries, taken as a whole.

                           (e)      Section 3.01(e) of the NBT Disclosure
Schedule sets forth a true, complete and correct list of all Corporate Entities
of which NBT or any NBT Subsidiary holds or beneficially owns 5% or more of the
outstanding shares of any class of voting securities, a general partnership
interest or other controlling interest, more than 24.9% of the outstanding
capital stock (whether voting or nonvoting) and subordinated debt or is
otherwise deemed to be a subsidiary within the meaning of the BHCA.


                                       25
<PAGE>   26

                  SECTION 3.02.  Certificate of Incorporation and Bylaws.

                  NBT and the NBT Subsidiaries have heretofore furnished or made
available to BSB a complete and correct copy of their respective Certificates of
Incorporation and Bylaws, as amended or restated. Such Certificates of
Incorporation and Bylaws are in full force and effect and none of NBT nor any
NBT Subsidiary is in violation of any of the provisions of its respective
Certificate of Incorporation or Bylaws.

                  SECTION 3.03.  Capitalization.

                           (a)      Capitalization of NBT. The authorized
capital stock of NBT as of March 31, 2000 consists of (i) 30,000,000 shares of
NBT Common Stock, of which 18,623,435 shares were issued and 18,100,868 were
outstanding, all of which are, and the shares of NBT Common Stock to be issued
pursuant to the Merger, when so issued will be, validly issued, fully paid and
non-assessable, and all of which have been or will be issued in compliance with
applicable securities laws, and (ii) 2,500,000 shares of preferred stock, par
value $0.01 per share ("NBT Preferred Stock"), of which no shares are issued and
outstanding. Since February 17, 2000, no shares of NBT Common Stock have been
issued. As of March 31, 2000, NBT had outstanding 1,172,575 options issued under
the NBT Stock Plans (as defined below), of which 560,400 were exercisable. No
options have been granted since January 24, 2000 to the date of this Agreement
under the NBT Stock Plans. As of the date of this Agreement, 522,567 shares of
the NBT Common Stock are held as treasury stock by NBT. Other than pursuant to
the NBT Rights Agreement, the NBT Stock Plans, the Agreement and Plan of Merger
with Pioneer American Holding Company Corp., dated December 7, 1999, as amended
as of March 7, 2000, the Agreement and Plan of Reorganization with M. Griffith
Inc., dated March 15, 2000, the NBT Stock Option Agreement, the 1994 Stock
Option Plan of Lake Ariel Bancorp, Inc., the 1997 Stock Option Plan of Lake
Ariel Bancorp, Inc., employment agreements between NBT and each of Daryl R.
Forsythe, Joe C. Minor, Martin A. Dietrich, John R. Bradley, and John G.
Martines (the "NBT Stock Plans"), and dividend reinvestment, employee stock
purchase and similar plans of NBT, there are no options, warrants or other
rights, rights of first refusal, agreements, arrangements, or commitments of any
character relating to the issued or unissued capital stock of NBT or obligating
NBT to issue or sell any shares of capital stock of, or other equity interests
in, NBT. Except as set forth in Schedule 3.03(b) of the NBT Disclosure Schedule,
there are no obligations, contingent or otherwise, of NBT to repurchase, redeem
or otherwise acquire any shares of NBT Common Stock or to provide funds to or
make any investment (in the form of a loan, capital contribution or otherwise)
in any other entity (including any NBT Subsidiary) other than pursuant to the
Rights Agreement, dated as of November 15, 1994, by and between NBT Bank and AST
("NBT Rights Agreement").

                           (b)      Capital Stock of the NBT Subsidiaries.
Except as set forth in Section 3.03(b) of the NBT Disclosure Schedule, there are
no options, warrants or other rights, rights of first refusal, agreements,
arrangements or commitments of any character relating to the issued or unissued
capital stock of the NBT Subsidiaries or obligating any NBT Subsidiary to issue
or sell any shares of capital stock of, or other equity interests in any NBT
Subsidiary. Except as set forth in Section 3.03(b) of the NBT Disclosure
Schedule, there are no obligations, contingent or otherwise, of any NBT
Subsidiary to


                                       26
<PAGE>   27
repurchase, redeem or otherwise acquire any shares of the capital stock of any
NBT Subsidiary or to provide funds to or make any investment (in the form of a
loan, capital contribution or otherwise) in any other entity.

                  SECTION 3.04.  Authority.

                           (a)      NBT has the requisite corporate power and
authority to execute and deliver this Agreement, to perform its obligations
hereunder and to consummate the transactions contemplated hereby. The execution
and delivery of this Agreement by NBT and the consummation by NBT of the
transactions contemplated hereby have been duly and validly authorized by all
necessary corporate action on the part of NBT and no other corporate proceedings
on the part of NBT are necessary to authorize this Agreement or to consummate
the transactions contemplated hereby (other than, with respect to the Merger,
the approval by the holders of a majority of the outstanding shares of NBT
Common Stock entitled to vote thereon of (A) this Agreement and the issuance of
NBT Common Stock in the Merger pursuant to this Agreement and (B) amendments to
NBT's Certificate of Incorporation to increase the number of shares of NBT
Common Stock that NBT is authorized to issue and to provide a new name for the
Surviving Corporation, in accordance with Delaware Law, the rules of the Nasdaq
Stock Market and NBT's Certificate of Incorporation and Bylaws). This Agreement
has been duly and validly executed and delivered by NBT and assuming the due
authorization, execution and delivery by BSB, constitutes the legal, valid and
binding obligation of NBT enforceable in accordance with its terms, except as
enforcement may be limited by bankruptcy, insolvency and similar laws affecting
creditors' rights and remedies generally and by general principles of equity.

                           (b)      The Board of Directors of NBT has taken all
actions necessary under Delaware Law and NBT's Certificate of Incorporation,
including approving the transactions contemplated herein, to insure that the
restrictions on business combinations set forth in Delaware Law do not or will
not apply to this Agreement, the transactions contemplated herein, the NBT Stock
Option Agreement or the transactions contemplated therein or any transaction
between BSB or its affiliates, on the one hand, and NBT or its affiliates, on
the other hand, following the exercise of the option granted under the NBT Stock
Option Agreement.

                  SECTION 3.05.  No Conflict; Required Filings and Consents.

                           (a)      Except as set forth in Section 3.05(a) of
the NBT Disclosure Schedule, the execution and delivery of this Agreement by NBT
does not, and the performance of this Agreement by NBT shall not, (i) conflict
with or violate the Certificate of Incorporation or Bylaws of NBT or any NBT
Subsidiary, (ii) conflict with or violate any Laws applicable to NBT or any NBT
Subsidiary, or by which its respective properties are bound or affected, or
(iii) result in any breach of or constitute a default (or an event that with
notice or lapse of time or both would become a default) under, or give to others
any rights of termination, amendment, acceleration or cancellation of, or result
in the creation of a Lien on any of the properties or assets of NBT or any NBT
Subsidiary pursuant to any note, bond, mortgage, indenture, contract, agreement,
lease, license, permit, franchise or other instrument or obligation to which NBT
or any NBT Subsidiary is a party or by which


                                       27
<PAGE>   28
NBT or any NBT Subsidiary or its respective properties are bound or affected,
except (in the case of clauses (ii) and (iii) of this Section 3.05(a)) for any
such conflicts, violations, breaches, defaults or other occurrences that would
not, either individually or in the aggregate, have a Material Adverse Effect on
NBT and the NBT Subsidiaries, taken as a whole.

                           (b)      The execution and delivery of this Agreement
by NBT does not, and the performance of this Agreement by NBT shall not, require
any Approvals, except (i) the filing of applications, notices and waiver
requests, as applicable, as to the Merger and the Bank Merger with the FRB under
the BHCA and OCC under the National Bank Act and the Bank Merger Act, and the
approval of the foregoing applications, notices and waiver requests; (ii) the
filing of any required applications or notices with the OCC as to the subsidiary
activities of BSB Bank, and the approval of the foregoing applications and
notices; (iii) courtesy notice of the Bank Merger to the NYSBD and, if deemed
necessary by the NYSBD, the filing of an application with the NYSBD for NBT to
become a bank holding company under New York law for a moment in time and the
approval of such application; (iv) the filing with the SEC of a registration
statement on Form S-4 to register the shares of NBT Common Stock to be issued in
connection with the Merger (including the shares of NBT Common Stock that may be
issued upon the exercise of the options referred to in Section 1.10 hereof),
which will include the Joint Proxy Statement, (v) the approval of this Agreement
by the requisite vote of the stockholders of BSB, (vi) the approval by NBT
stockholders of (A) this Agreement and the issuance of NBT Common Stock in the
Merger pursuant to this Agreement and (B) the amendments to NBT's Certificate of
Incorporation to increase the number of shares of NBT Common Stock that NBT is
authorized to issue and to provide a new name for the Surviving Corporation;
(vii) the filing of the Certificate of Merger with the Secretary of State of
Delaware pursuant to the Delaware Law, (viii) the filings required by the
National Bank Act and OCC Regulations, (ix) the filings required by NASDAQ to
list additional shares, (x) such consents, approvals, orders, authorizations,
registrations, declarations and filings as may be required under applicable
federal, foreign and state securities (or related) laws and, if applicable, the
HSR Act, and the securities or antitrust laws of any foreign country, and (xi)
such filings, authorizations or approvals as may be set forth in Section 3.05(b)
of the NBT Disclosure Schedule. No consents or approvals of or filings or
registrations with any Governmental Entity, or with any third party are
necessary in connection with (1) the execution and delivery by NBT of this
Agreement and the NBT Stock Option Agreement, (2) the consummation by NBT of the
Merger and the other transactions contemplated hereby, (3) the execution and
delivery by NBT Bank of the Bank Merger Agreement, (4) the performance by NBT of
its obligations under the NBT Stock Option Agreement; and (5) the consummation
by NBT Bank of the Bank Merger and the transactions contemplated thereby,
except, in each case, for such consents, approvals or filings, the failure of
which to obtain will not have a Material Adverse Effect on the ability of NBT to
consummate the transactions contemplated hereby.

                           (c)      NBT hereby represents to BSB that it has no
knowledge of any reason why approval or effectiveness of any of the
applications, notice or filings referred to in Section 3.05 cannot be obtained
or granted on a timely basis.


                                       28
<PAGE>   29

                  SECTION 3.06.  Compliance.

                  Neither NBT nor any NBT Subsidiary is in conflict with, or in
default or violation of, (i) any Law applicable to NBT or the NBT Subsidiaries
or by which any of their respective properties are bound or affected, or (ii)
any note, bond, mortgage, indenture, contract, agreement, lease, license,
permit, franchise or other instrument or obligation to which NBT or any NBT
Subsidiary is a party or by which NBT or any NBT Subsidiary or any of their
respective properties are bound or affected, except for any such conflicts,
defaults or violations which would not, either individually or in the aggregate,
have a Material Adverse Effect on NBT and the NBT Subsidiaries, taken as a
whole.

                  SECTION 3.07.  Securities and Banking Reports; Financial
                  Statements.

                           (a)      NBT and the NBT Subsidiaries have filed all
material forms, reports, registrations, statements and documents, together with
any amendments required to be made with respect thereto that were required to be
filed since January 1, 1995 with the Regulatory Agencies and all Other Reports
required to be filed by NBT and any NBT Subsidiary since January 1, 1995, and
paid all fees and assessments due and payable in connection therewith, except,
in the case of the Other Reports, where failure to file such form, report,
registration, statement or document or pay such fees and assessments would not,
either individually or in the aggregate, have a Material Adverse Effect on NBT
and the NBT Subsidiaries, taken as a whole (all such reports, registrations,
statements and documents are collectively referred to as the "NBT Reports"). The
NBT Reports, including all NBT Reports filed after the date of this Agreement,
(i) were, or will be, prepared in accordance with the requirements of applicable
Law and (ii) did not at the time they were filed, or will not at the time they
are filed, contain any untrue statement of material fact or omit to state a
material fact required to be stated therein or necessary in order to make the
statements therein, in the light of the circumstances under which they were
made, not misleading.

                           (b)      Each of the consolidated financial
statements (including, in each case, any related notes thereto) contained in any
filings with the SEC since January 1, 1995 (the "NBT SEC Reports"), including
any NBT SEC Reports filed since the date of this Agreement and prior to or at
the Effective Time, have been, or will be, prepared in accordance with GAAP
throughout the periods involved (except as may be indicated in the notes
thereto) and each fairly presents, or will fairly present, in all material
respects, the consolidated financial position of NBT and the NBT Subsidiaries as
of the respective dates thereof and the consolidated results of its operations
and changes in financial position for the periods indicated, except that any
unaudited interim financial statements were or are subject to normal and
recurring year-end adjustments which were not or are not expected to be material
in amount.

                           (c)      Except as and to the extent set forth on the
consolidated balance sheet of NBT and the NBT Subsidiaries as of December 31,
1999, including all notes thereto (the "NBT Balance Sheet"), neither NBT nor any
NBT Subsidiary has any liabilities or obligations of any nature (whether
accrued, absolute, contingent or otherwise), except for (i) liabilities or
obligations incurred in the ordinary course of business since December 31, 1999
or by operation of law in the merger with Lake Ariel Bancorp, Inc. on


                                       29
<PAGE>   30

February 17, 2000 and (ii) liabilities or obligations that would not, either
individually or in the aggregate, have a Material Adverse Effect on NBT and the
NBT Subsidiaries, taken as a whole.

                  SECTION 3.08.  Absence of Certain Changes or Events.

                           Except as disclosed in the NBT SEC Reports filed
prior to the date of this Agreement, since December 31, 1999, (a) NBT and the
NBT Subsidiaries have conducted their businesses only in the ordinary course and
in a manner consistent with past practice and (b) there has been no event which
has had, or is reasonably likely to result in, either individually or in the
aggregate, a Material Adverse Effect on NBT and the NBT Subsidiaries, taken as a
whole.

                  SECTION 3.09.  Absence of Litigation and Agreements.

                           (a)      Except as disclosed in the NBT SEC Reports
filed prior to the date of this Agreement or set forth in Section 3.09 of the
NBT Disclosure Schedule, (i) neither NBT nor any NBT Subsidiary is subject to
any continuing order of, or written agreement or memorandum of understanding
with, or continuing investigation by, any federal or state savings and loan or
bank regulatory authority or other governmental entity or regulatory authority,
or any judgment, order, writ, injunction, decree or award of any governmental
entity or regulatory authority or arbitrator, including, without limitation,
cease-and-desist or other orders which, either individually or in the aggregate,
would have or reasonably be expected to have a Material Adverse Effect on NBT
and the NBT Subsidiaries, taken as a whole; (ii) there is no claim of any kind,
action, suit, litigation, proceeding, arbitration, investigation, or controversy
affecting NBT or the NBT Subsidiaries pending or, to the knowledge of NBT,
threatened, except (A) as of the date of this Agreement, for matters which
individually seek damages not in excess of $500,000 and (B) as of the Closing,
for matters which otherwise cannot reasonably be expected to have, either
individually or in the aggregate, a Material Adverse Effect on NBT and the NBT
Subsidiaries, taken as a whole; and (iii) there are not uncured violations, or
violations with respect to which refunds or restitutions may be required, cited
in any compliance report to NBT or the NBT Subsidiaries as a result of the
examination by any bank regulatory authority, which would have or reasonably be
expected to have, either individually or in the aggregate, a Material Adverse
Effect on NBT and the NBT Subsidiaries, taken as a whole.

                           (b)      Except as set forth on the NBT Disclosure
Schedule at Section 3.09, neither NBT nor any of the NBT Subsidiaries is a party
to any written agreement or memorandum of understanding with, or party to any
commitment letter, board resolution submitted to a regulatory authority or
similar undertaking to, or is subject to any order or directive by, or is a
recipient of any extraordinary supervisory letter from any governmental entity
or agency which restricts materially the conduct of its business, or in any
manner relates to its capital adequacy, its credit or reserve policies or its
management nor has NBT or any NBT Subsidiary (i) been advised by any
governmental entity or agency that it is contemplating issuing or requesting (or
is considering the appropriateness of issuing or requesting) any such order,
decree, agreement, memorandum of understanding, extraordinary supervisory
letter, commitment letter or similar


                                       30
<PAGE>   31

submission or (ii) have knowledge of any pending or threatened regulatory
investigation. Neither NBT nor any NBT Subsidiary is required by Section 32 of
the Federal Deposit Insurance Act to give prior notice to a Federal banking
agency of the proposed addition of an individual to its board of directors or
the employment of an individual as a senior executive officer.

                  SECTION 3.10.  Employee Benefit Plans.

                  (a)      Section 3.10 of the NBT Disclosure Schedule sets
forth a true and complete list of all benefit plans, arrangements, commitments
and payroll practices (whether or not employee benefit plans ("NBT Plans" or
"Plan") as defined in Section 3(3) of ERISA, including, without limitation, sick
leave, vacation pay, severance pay, salary continuation for disability,
consulting or other compensation arrangements, retirement, deferred
compensation, bonus, incentive compensation, stock purchase, stock option,
health, including hospitalization, medical and dental, life insurance and
scholarship programs maintained as of the date of this Agreement, or within the
last six years of the date of this Agreement, for the benefit of any present or
former employees of NBT, any of the NBT Subsidiaries or any other entity which
together with NBT would be deemed a "single employer" within the meaning of
Section 4001 of ERISA or Code Section 414(b), (c), (m) or (o) ("NBT ERISA
Affiliate") or to which NBT or any NBT ERISA Affiliate has contributed or is or
was within the last six years obligated to make payments.

                  (b)      With respect to each NBT Plan, NBT has heretofore
delivered or made available to BSB true, correct and complete copies of the plan
document, trust agreement, if any, all insurance policies, if any, and all
material related documents, including, but not limited to, (i) the actuarial
report for each NBT Plan that is a defined benefit plan, funded welfare plan or
other plan requiring actuarial valuation for each of the last five years, (ii)
the most recent determination letter from the IRS, if such NBT Plan is intended
to be a qualified plan under Section 401(a) of the Code, (iii) the current
summary plan description and each summary of material modification, (iv) each
Form 5500 series filed for the preceding five plan years, (v) each agreement
with each fiduciary and service provider relating to such NBT Plan, and (vi) all
substantive correspondence relating to such NBT Plan addressed to or received
from the IRS, the DOL, PBGC or any other governmental agency, (vii) each bond
required by Section 412 of ERISA, each fiduciary liability insurance policy, and
each agreement to indemnify any fiduciary, including each amendment to any such
document.

                  (c)      Except as set forth in Section 3.10(c) of the NBT
Disclosure Schedule:

                           (i)      Each NBT Plan has been operated and
administered in all material respects in compliance with the terms of its
governing document(s) and instrument(s) and applicable Laws, including, but not
limited to, ERISA and the Code, and the funding, filing, termination, reporting
and disclosure and continuation coverage obligations pursuant to Title V of
COBRA;

                           (ii)     Each NBT Plan that is intended to be
"qualified" within the meaning of Section 401(a) of the Code is and from its
inception has been so qualified, and any trust created pursuant to any such Plan
is exempt from federal income tax under Section 501(a) of the Code, each such
Plan has received from the IRS a favorable


                                       31
<PAGE>   32

determination letter to such effect upon which NBT or an NBT ERISA Affiliate is
entitled to rely as to such matters and which is currently applicable, and
neither NBT nor any NBT ERISA Affiliate is aware of any circumstance or event
which would jeopardize the tax-qualified status of any NBT Plan or the
tax-exempt status of any related trust, or which would cause the imposition of
any liability, penalty or tax under ERISA or the Code with respect to any NBT
Plan;

                           (iii)    With respect to each NBT Plan that is
subject to Title IV of ERISA, the present value of accrued benefits under such
NBT Plan, based upon the actuarial assumptions used by the PBGC to determine the
level of funding required in the event of termination of such Plan, did not, as
of its latest valuation date, exceed the then current value of the assets of
such Plan allocable to such accrued benefits;

                           (iv)     No NBT Plan provides benefits, including,
without limitation, death or medical benefits (whether or nor insured), with
respect to current or former employees of NBT or any NBT ERISA Affiliate beyond
their retirement or other termination of employment with NBT or an NBT ERISA
Affiliate, other than coverage mandated by applicable Law, death benefits or
retirement benefits under a Plan that is an "employee pension plan," as defined
by Section 3(2) of ERISA, deferred compensation benefits under an NBT Plan that
are accrued as liabilities on the books of NBT or any NBT ERISA Affiliate, or
benefits the full cost of which is borne by the current or former employee (or
his beneficiary);

                           (v)      No liability under Title IV of ERISA has
been incurred by NBT or any NBT ERISA Affiliate that has not been satisfied in
full as of the date of this Agreement, and no condition exists that presents a
material risk of NBT or any NBT ERISA Affiliate incurring a material liability
thereunder;

                           (vi)     No NBT Plan is a "multiemployer plan," as
such term is defined in Section 3(37) of ERISA, nor has NBT or any NBT ERISA
Affiliate ever had any obligation to contribute to a multiemployer plan or
otherwise incurred or assumed any liability for complete or partial withdrawal
from such a plan that is a pension plan subject to Title IV of ERISA.

                           (vii)    All contributions or other amounts payable
by NBT or any NBT ERISA Affiliate as of the Effective Time with respect to each
NBT Plan, and all other liabilities of each such entity with respect to such NBT
Plan, with respect to current or prior plan years, have been paid or accrued in
accordance with GAAP and Section 412 of the Code;

                           (viii)   Neither NBT nor any NBT ERISA Affiliate nor
any NBT Plan has engaged in any transaction with respect to which any of the
aforementioned entities could be subject to either a civil liability or civil
penalty assessed pursuant to Section 409, 501(i) or 502(1) of ERISA or a tax
imposed pursuant to Section 4975 or 4976 of the Code;

                           (ix)     There are, and for the past three years
there have been, no inquiries, proceedings, claims, suits pending or, to the
knowledge of NBT, threatened (other than routine claims for benefits) by any
governmental agency or authority or by any participant or beneficiary against
any of the NBT Plans, the assets of any of the trusts


                                       32
<PAGE>   33

under such Plans or the Plan sponsor or the Plan administrator, or against any
fiduciary of any of such NBT Plans with respect to the design or operation of an
NBT Plan;

                           (x)      Each NBT Plan could be terminated as of the
Effective Time without material liability to NBT or any NBT ERISA Affiliate in
excess of the amount accrued with respect to such Plan on the financial
statements of NBT or such NBT ERISA Affiliate;

                           (xi)     No NBT Plan, either individually or
collectively, provides for any payments by NBT or any NBT ERISA Affiliate that
would not be deductible under Code Sections 162(a)(1), 162(m) or 404, or that
would, after giving effect to the transactions contemplated by this Agreement,
constitute an "excess parachute payment" within the meaning of Code Section
280G, nor would the transactions contemplated by this Agreement accelerate the
time of payment or vesting, or increase the amount of compensation due to any
employee;

                           (xii)    No "accumulated funding deficiency" as
defined in Section 302(a)(2) of ERISA or Section 412 of the Code, whether or not
waived, and no "unfunded current liability" as determined under Section 412(1)
of the Code exists with respect to any NBT Plan subject to Section 412 of the
Code and Section 302 of ERISA, and there are no unsatisfied liabilities to
participants, the IRS, the DOL or the PBGC as a result of the termination of any
NBT Plan other than any such liabilities that have not become due or that are
being contested in good faith;

                           (xiii)   No NBT Plan has experienced a "reportable
event" (as such term is defined in Section 4043(b) of ERISA) that is not subject
to an administrative or statutory waiver from the reporting requirement;

                           (xiv)    All reports and information required to be
filed with the DOL, IRS and PBGC or with plan participants and their
beneficiaries with respect to each NBT Plan have been filed, and all annual
reports (including Form 5500 series) of such Plans were certified without
qualification by each Plan's accountants and actuaries. Any annual reports which
are not yet due but are required to be filed with respect to a plan year which
ended on or prior to the Effective Date and any annual reports which are
required to be filed with respect to current plan years shall be filed on a
timely basis.

                           (xv)     Any bond required under ERISA with respect
to any NBT Plan has been obtained and is in full force and effect and no funds
held by or under the control of NBT are plan assets of any NBT Plan.

                  SECTION 3.11.  Material Contracts.

                  Except as set forth in Section 3.11 of the NBT Disclosure
Schedule, as of the date of this Agreement, neither NBT nor any NBT Subsidiary
is a party to or bound by (a) any contract or commitment for capital
expenditures in excess of $500,000 for any one project, (b) contracts or
commitments for the purchase of materials or supplies or for the performance of
services over a period of more than 60 days from the date of this Agreement and
calling for aggregate future payments of $1,000,000 or more during the term of
such contract or commitment, (c) any contract which is a "material contract" (as
such term is


                                       33
<PAGE>   34

defined in Item 601(b)(10) of Regulation S-K of the SEC) that has not been filed
or incorporated by reference in the NBT SEC Reports, (d) any contract which
contains non-compete or exclusivity provisions or restrictions with respect to
any business or geographic area or (e) any contract which would prohibit or
materially delay the consummation of the Merger or any other transaction
contemplated by this Agreement. Each contract, arrangement, commitment or
understanding of the type described in this Section 3.11, whether or not set
forth in Section 3.11 of NBT Disclosure Schedule, is referred to herein as an
"NBT Contract". Neither NBT nor any NBT Subsidiary knows of, or has received
notice of, any violation of any NBT Contract by any of the other parties
thereto, except for violations which, individually or in the aggregate, would
not result in a Material Adverse Effect on NBT and NBT Subsidiaries, taken as a
whole.

                  SECTION 3.12.  Environmental Matters.

                           (a)      Each of NBT and the NBT Subsidiaries is in
compliance in all material respects with all applicable federal and state laws
and regulations relating to pollution or protection of the environment
(including without limitation, laws and regulations relating to emissions,
discharges, releases and threatened releases of Hazardous Materials, or
otherwise relating to the manufacture, processing, distribution, use, treatment,
storage, disposal, transport or handling of Hazardous Materials.

                           (b)      There is no suit, claim, action, proceeding,
investigation or notice pending or, to the knowledge of NBT, threatened (or, to
the knowledge of NBT, past or present actions or events that could form the
basis of any such suit, claim, action, proceeding, investigation or notice), in
which NBT or any NBT Subsidiary has been or, with respect to threatened suits,
claims, actions, proceedings, investigations or notices may be, named as a
defendant (i) for alleged material noncompliance (including by any predecessor),
with any environmental law, rule or regulation or (ii) relating to any material
release or threatened release into the environment of any Hazardous Material,
occurring at or on a site owned, leased or operated by NBT or any NBT
Subsidiary, or to the knowledge of NBT relating to any material release or
threatened release into the environment of any Hazardous Material, occurring at
or on a site not owned, leased or operated by NBT or any NBT Subsidiary.

                           (c)      During the period of NBT's or any NBT
Subsidiary's ownership or operation of any of its properties, there has not
been, to NBT's knowledge, any material release of Hazardous Materials in, on,
under or affecting any such property.

                           (d)      To the knowledge of NBT, neither NBT nor any
NBT Subsidiary has made or participated in any loan to any person who is subject
to any suit, claim, action, proceeding, investigation or notice, pending or
threatened, with respect to (i) any alleged material noncompliance as to any
property securing such loan with any environmental law, rule or regulation, or
(ii) the release or the threatened release into the environment of any Hazardous
Material at a site owned, leased or operated by such person on any property
securing such loan.


                                       34
<PAGE>   35

                  SECTION 3.13.  Taxes.

                           Each of NBT and the NBT Subsidiaries has duly filed
all Tax Returns required to be filed by it on or prior to the date hereof (all
such returns being accurate and complete in all material respects) and has duly
paid or made provision on the financial statements referred to in Sections 3.07
and 5.15 hereof in accordance with GAAP for the payment of all material Taxes
which have been incurred or are due or claimed to be due from it by Taxing
Authorities on or prior to the date hereof other than Taxes (a) which (x) are
not yet delinquent or (y) are being contested in good faith and set forth in
Section 3.13 of the NBT Disclosure Schedule and (b) which have not been finally
determined. All liability with respect to the Tax Returns of NBT and the NBT
Subsidiaries has been satisfied for all years to and including 1998. The IRS has
not notified NBT of, or otherwise asserted, that there are any material
deficiencies with respect to the federal income Tax Returns of NBT subsequent to
tax year 1995. There are no material disputes pending, or claims asserted for
Taxes or assessments upon NBT or any NBT Subsidiary, nor has NBT nor any NBT
Subsidiary been requested to give any currently effective waivers extending the
statutory period of limitation applicable to any federal or state income Tax
Return for any period. In addition, Tax Returns which are accurate and complete
in all material respects have been filed by NBT and the NBT Subsidiaries for all
periods for which returns were due with respect to income tax withholding,
Social Security and unemployment taxes and the amounts shown on such Tax Returns
to be due and payable have been paid in full or adequate provision therefor in
accordance with GAAP has been included by NBT in the financial statements
referred to in Sections 3.07 and 5.15 hereof. All NBT Tax Returns relating to
federal income taxes have been examined by the relevant Taxing Authorities, or
closed without audit by applicable statutes of limitations, and all deficiencies
proposed as a result of such examinations have been paid or settled, for all
periods before and including the taxable year ended 1995. Except as set forth in
Section 3.13 of the NBT Disclosure Schedule, neither NBT nor any NBT Subsidiary
has consented to any waiver or extension of any statute of limitations with
respect to any Tax. Neither NBT nor any NBT Subsidiary has made an election
under Section 341(f) of the Code. NBT has provided or made available to BSB
complete and correct copies of its Tax Returns and all material correspondence
and documents, if any, relating directly or indirectly to taxes for each taxable
year or other relevant period as to which the applicable statute of limitations
has not run on the date hereof. For this purpose, "correspondence and documents"
include, without limitation, amended Tax Returns, claims for refunds, notices
from Taxing Authorities of proposed changes or adjustments to Taxes or Tax
Returns, consents to assessment or collection of Taxes, acceptances of proposed
adjustments, closing agreements, rulings and determination letters and requests
therefor, and all other written communications to or from Taxing Authorities
relating to any material Tax liability of NBT or any NBT Subsidiary. NBT will
not be a "foreign person" as that term is used in Section 1.1445-2 of the
Treasury Regulations promulgated under the Code. NBT Bank is not a "United
States real property holding corporation" within meaning of Section 897 of the
Code and was not a "United States real property holding corporation" on any
"determination date" (as defined in Section 1.897-2(c) of such Regulations) that
occurred during any relevant period.

                  SECTION 3.14.  Affiliates.


                                       35
<PAGE>   36

                  Each director, executive officer and other person who is an
"affiliate" (for purposes of Rule 145 under the Securities Act, and for purposes
of qualifying the Merger for "pooling-of-interests" accounting treatment) of NBT
is listed at Section 3.14 of the NBT Disclosure Schedule, and except as
indicated thereon, each such person has delivered to BSB concurrently with the
execution of this Agreement, a stockholder agreement in the form of Exhibit G
hereto (the "NBT Stockholder Agreement").

                  SECTION 3.15.  Derivative Instruments.

                  All Derivative Instruments to which NBT or any NBT Subsidiary
is a party or to which any of their properties or assets may be subject were
entered into in the ordinary course of business and, to the knowledge of NBT, in
accordance with prudent banking practice and applicable rules, regulations, and
policies of the regulatory agencies and with counterparties believed to be
financially responsible at the time and, to knowledge of NBT, are legal, valid,
and binding obligations enforceable in accordance with their terms (except as
may be limited by bankruptcy, insolvency, moratorium, reorganization, or similar
laws affecting the rights of creditors generally, and the availability of
equitable remedies), and, to the knowledge of NBT, are in full force and effect.
NBT and each NBT Subsidiary has duly performed in all material respects all of
its obligations under any such Derivative Instruments, and to the knowledge of
NBT, there are no breaches, violations, or defaults or allegations or assertions
of such by any party thereunder except for any such breaches, violations, or
defaults or allegations or assertions which would not, individually or in the
aggregate, have a Material Adverse Effect on NBT and the NBT Subsidiaries, taken
as a whole.

                  SECTION 3.16.  Regulatory Approvals.

                  NBT is not aware of any aspect of, or issues relating to, its
or the NBT Subsidiaries' operations and business that would prevent the
condition of Closing set forth in Section 6.01(c) from being satisfied.

                  SECTION 3.17.  Brokers.

                  Except as contemplated by or referenced in the April 12, 2000
letter agreement between McConnell, Budd & Downes, Inc. ("MBD") and NBT, a true
and complete copy of which NBT has delivered to BSB, no broker, finder or
investment banker is entitled to any brokerage, finder's or other fee or
commission in connection with the transactions contemplated by this Agreement
based upon arrangements made by or on behalf of NBT or any NBT Subsidiary.

                  SECTION 3.18.  Pooling of Interest and Tax Matters.

                  Neither NBT nor, to the knowledge of NBT, any of its
affiliates (as defined in Section 2.14) has through the date of this Agreement
taken or agreed to take any action that would prevent NBT from accounting for
the business combination to be effected by the Merger and the Bank Merger as a
pooling of interests in accordance with GAAP or would prevent the Merger from
qualifying as a reorganization under Section 368(a) of the Code. NBT has no
reason to believe that the Merger will not qualify as a pooling of interests or
as a reorganization under Section 368(a) of the Code.


                                       36
<PAGE>   37

                  SECTION 3.19.  Votes Required.

                  The requisite affirmative votes of holders of a majority of
the outstanding shares of NBT Common Stock entitled to vote with respect to the
approval of this Agreement and the issuance of NBT Common Stock in the Merger
pursuant to this Agreement and the amendments to NBT's Certificate of
Incorporation to increase the number of shares of NBT Common Stock that NBT is
authorized to issue and to provide a new name for the Surviving Corporation are
the only votes of the holders of any class or series of NBT's capital stock
required in connection with the Merger.

                  SECTION 3.20.  Fairness Opinion.

                  NBT has received an opinion of MBD on or prior to the date of
this Agreement to the effect that, as of the date of such opinion, the Exchange
Ratio is fair to the stockholders of NBT, from a financial point of view ("NBT
Fairness Opinion") and MBD has consented to the inclusion of the NBT Fairness
Opinion in the Registration Statement.

                  SECTION 3.21.  Rights Agreement

                  The Board of Directors of NBT has taken such action as is
necessary to render the NBT Rights Agreement inapplicable to the Merger and the
other transactions contemplated by this Agreement.

                                   ARTICLE IV

                            COVENANTS OF BSB AND NBT

                  SECTION 4.01.  Affirmative Covenants.

                           (a)      Each of BSB and NBT hereby covenants and
agrees with the other that prior to the Effective Time, unless the prior written
consent of the other shall have been obtained and except as otherwise
contemplated herein, BSB will, and will cause each BSB Subsidiary to, and NBT
will, and will cause each NBT Subsidiary to, conduct their respective businesses
in the ordinary course of business in a manner consistent with past practice,
use their respective reasonable best efforts to preserve intact their respective
business organizations, keep available the services of their respective current
officers, employees and consultants and to preserve their respective current
business relationships.

                           (b)      Notwithstanding that BSB believes that it
has established all reserves and taken all provisions for possible loan losses
required by GAAP and applicable laws, rules and regulations, BSB recognizes that
NBT may have adopted different loan, accrual and reserve policies (including
loan classifications and levels of reserves for possible loan losses). In that
regard, BSB shall establish such additional accruals and reserves as may be
necessary to conform the accounting and credit loss reserve practices and
methods of BSB to those of NBT, provided, that no such action need be effected
until


                                       37
<PAGE>   38

the parties receive all necessary governmental and stockholder approvals and
consents to consummate the transactions contemplated hereby.

                  SECTION 4.02.  Negative Covenants.

                  Except as set forth in Section 4.02 of the BSB Disclosure
Schedule or the NBT Disclosure Schedule, as applicable, and except as
specifically contemplated by this Agreement, from the date of this Agreement
until the Effective Time, each of BSB and NBT shall not do, and, in the case of
BSB, permit the BSB Subsidiaries to do, and, in the case of NBT, permit the NBT
Subsidiaries to do, without the prior written consent of NBT or BSB, as
applicable, any of the following:

                           (a)      adjust, split, combine or reclassify any
capital stock, declare or pay any dividend on, or make any other distribution in
respect of, its outstanding shares of capital stock, except for quarterly
dividends or, in the case of the periodic stock dividends of NBT, annual
declarations and payments in accordance with past practice and in per share
amounts not in excess of historical per share dividend amounts; provided,
however, that after the date of this Agreement, each of NBT and BSB shall
coordinate with the other the declaration of any cash dividends in respect of
NBT Common Stock and BSB Common Stock and the record dates and payment dates
relating thereto, it being the intention of the parties hereto that holders of
NBT Common Stock and BSB Common Stock shall not receive two cash dividends, or
fail to receive one cash dividend, for any quarter with respect to their shares
of NBT Common Stock and/or BSB Common Stock and any shares of NBT Common Stock
any such holder receives in exchange therefor in the Merger;

                           (b)      (i) redeem, purchase or otherwise acquire
any shares of its capital stock or any securities or obligations convertible
into or exchangeable for any shares of its capital stock, or any options,
warrants, conversion or other rights to acquire any shares of its capital stock
or any such securities or obligations, (ii) effect any reorganization or
recapitalization, (iii) purchase or otherwise acquire any assets or stock of any
corporation, bank or other business for consideration which in the aggregate
exceeds $10 million, except that such amount shall be $30 million in the case of
any such transaction as to which NBT gives BSB advance written notice and the
opportunity to confer and that would not delay the transaction contemplated by
this Agreement, or (iv) liquidate, sell, dispose of or encumber any assets for
consideration which in the aggregate exceeds $25 million (except for bank
borrowings and operations in the ordinary course);

                           (c)      issue, deliver, award, grant or sell, or
authorize or propose the issuance, delivery, award, grant or sale of, any shares
of any class of its capital stock (including shares held in treasury) or any
rights, warrants or options to acquire, any such shares;

                           (d)      propose or adopt any amendments to its
certificate of incorporation or bylaws;

                           (e)      change any of its methods of accounting in
effect at December 31, 1999, or change any of its methods of reporting income or
deductions for federal income


                                       38
<PAGE>   39

tax purposes from those employed in the preparation of the federal income tax
returns for the taxable year ending December 31, 1998, except as may be required
by law or GAAP;

                           (f)      other than in the ordinary course of
business consistent with past practice, or by operation of law in connection
with merger transactions set forth in Section 4.02 of the NBT Disclosure
Schedule, incur any indebtedness for borrowed money (other than (x) short-term
indebtedness incurred to refinance short-term indebtedness or (y) indebtedness
among its corporate affiliates), or assume, guarantee, endorse or otherwise as
an accommodation become responsible for the obligations of any other individual,
corporation or other entity;

                           (g)      except for transactions in the ordinary
course of business consistent with past practice, and except for agreements
entered into or terminated in connection with merger transactions set forth in
Section 4.02 of the NBT Disclosure Schedule (other than any such termination by
mutual agreement of the parties), enter into or terminate any material contract
or agreement, or make any change in any of its material leases or material
contracts, other than renewals of such contracts and leases without material
adverse changes of terms;

                           (h)      increase in any manner the compensation or
fringe benefits of any of its employees, except as required by existing plans or
agreements or pay any pension or retirement allowance not required by any
existing plan or agreement to any such employees or become a party to, adopt,
terminate, amend or commit itself to any pension, retirement, profit sharing or
welfare benefit plan or agreement or employment agreement with or for the
benefit of any employee other than, in each case, in the ordinary course of
business consistent with past practice, or except as required by existing plans
or agreements, or accelerate the vesting of any deferred compensation, stock
options or other stock-based compensation;

                           (i)      settle any claim, action or proceeding
involving money damages, except in the ordinary course of business consistent
with past practices;

                           (j)      take any action that would prevent or impede
the Merger from qualifying (i) for pooling of interests accounting treatment or
(ii) as a reorganization within the meaning of Section 368 of the Code:
provided, however, that nothing contained herein shall limit the ability of NBT
or BSB to exercise its rights under the BSB Stock Option Agreement or the NBT
Stock Option Agreement, respectively;

                           (k)      take any action that is intended or may
reasonably be expected to result in any of its representations and warranties
set forth in this Agreement being or becoming untrue in any material respect at
any time prior to the Effective Time, or in any of the conditions to the Merger
set forth in Article VI not being satisfied or in a violation of any provision
of this Agreement, except, in each case, as may be required by applicable law;

                           (l)      take any action or fail to take any action
which individually or in the aggregate can be reasonably expected to have a
Material Adverse Effect on, in the case of BSB, BSB and the BSB Subsidiaries,
taken as a whole or, in the case of NBT, NBT and the NBT Subsidiaries, taken as
a whole; or


                                       39
<PAGE>   40

                           (m)      agree in writing or otherwise to do any of
the foregoing.

                                    ARTICLE V

                              ADDITIONAL AGREEMENTS

                  SECTION 5.01.  Registration Statement; Joint Proxy Statement.

                           (a)      As promptly as practicable after the
execution of this Agreement, (i) BSB and NBT shall prepare the Joint Proxy
Statement which shall constitute the joint proxy statement of BSB and NBT and
the prospectus of NBT relating to the meetings of BSB's and NBT's stockholders
to be held to consider approval and adoption of this Agreement and, with respect
to NBT, related amendments to its Certificate of Incorporation, and (ii) NBT
shall prepare and file with the SEC a registration statement on Form S-4
(together with any amendments thereto, the "Registration Statement") which shall
include the Joint Proxy Statement, with respect to the registration of the
shares of NBT Common Stock to be issued to the stockholders and option holders
of BSB in the Merger. NBT and BSB shall each use its reasonable best efforts to
cause the Registration Statement to become effective as soon as reasonably
practicable. BSB will furnish to NBT all information concerning BSB and the BSB
Subsidiaries required to be set forth in the Registration Statement and NBT will
provide BSB and its counsel the opportunity to review such information as set
forth in the Registration Statement and Joint Proxy Statement. NBT and BSB will
each render to the other its full cooperation in preparing, filing, prosecuting
the filing of, and amending the Registration Statement such that it comports at
all times with the requirements of the Securities Act and the Securities
Exchange Act of 1934, as amended (the "Exchange Act"). Each of NBT and BSB will
promptly advise the other if at any time prior to the Effective Time any
information provided by it for inclusion in the Registration Statement or the
Joint Proxy Statement appears to have been, or shall have become, incorrect or
incomplete and will furnish the information necessary to correct such
misstatements or omissions. As promptly as practicable after the Registration
Statement shall have become effective, each of BSB and NBT will mail the Joint
Proxy Statement to its respective stockholders. NBT shall also take any action
required to be taken under any applicable blue sky laws in connection with the
issuance of the shares of NBT Common Stock to be issued as set forth in this
Agreement and BSB and the BSB Subsidiaries shall furnish all information
concerning BSB, the BSB Subsidiaries and the holders of Shares and other
assistance as NBT may reasonably request in connection with such action.

                           (b)      (i)  The Joint Proxy Statement shall include
the recommendation of the Board of Directors of BSB to the stockholders of BSB
in favor of approval and adoption of this Agreement; provided, however, that, in
connection with recommending approval of a Superior Competing Transaction (as
defined in Section 5.05), the Board of Directors of BSB may, at any time prior
to such time as the stockholders of BSB shall have adopted and approved this
Agreement in accordance with Delaware Law, withdraw, modify or change any such
recommendation to the extent that the Board of Directors of BSB determines in
good faith, after consultation with and based upon the advice of independent
legal counsel, that the failure to so withdraw, modify or change its


                                       40
<PAGE>   41

recommendation would cause the Board of Directors of BSB to breach its fiduciary
duties to BSB's stockholders under applicable law and, notwithstanding anything
to the contrary contained in this Agreement, any such withdrawal, modification
or change of recommendation shall not constitute a breach of this Agreement by
BSB.

                                    (ii)    The Joint Proxy Statement shall
include the recommendation of the Board of Directors of NBT to the stockholders
of NBT in favor of approval and adoption of this Agreement and the issuance of
NBT Common Stock in the Merger pursuant to the Agreement and the amendment of
NBT's Certificate of Incorporation to increase the number of shares of NBT
Common Stock that NBT is authorized to issue and to provide for a new name for
the Surviving Corporation; provided, however, that, in connection with
recommending approval of a Superior Competing Transaction, the Board of
Directors of NBT may, at any time prior to such time as the stockholders of NBT
shall have adopted and approved this Agreement in accordance with Delaware Law
withdraw, modify, or change any such recommendation to the extent that the Board
of Directors of NBT determines in good faith, after consultation with and based
upon the advice of independent legal counsel, that the failure to so withdraw,
modify or change its recommendation would cause the Board of Directors of NBT to
breach its fiduciary duties to NBT's stockholders under applicable law and,
notwithstanding anything to the contrary contained in this Agreement, any such
withdrawal, modification or change of recommendation shall not constitute a
breach of this Agreement by NBT.

                           (c)      Notwithstanding any withdrawal, modification
or change in any approval or recommendation of the Board of Directors of BSB or
NBT, as the case may be, each of BSB and NBT agree to hold their respective
Stockholders' Meetings in accordance with the time period specified in Section
5.02.

                           (d)      No amendment or supplement to the Joint
Proxy Statement or the Registration Statement will be made by NBT or BSB without
the approval of the other party (which will not be unreasonably withheld or
delayed). NBT and BSB each will advise the other, promptly after it receives
notice thereof, of the time when the Registration Statement has become effective
or any supplement or amendment has been filed, the issuance of any stop order,
the suspension of the qualification of the NBT Common Stock issuable in
connection with the Merger for offering or sale in any jurisdiction, or any
request by the SEC for amendment of the Joint Proxy Statement or the
Registration Statement, or comments thereon and responses thereto or requests by
the SEC for additional information.

                           (e)      NBT shall as promptly as reasonably
practicable prepare and submit to the NASDAQ a listing application covering the
shares of NBT Common Stock issuable in the Merger and the shares of NBT Common
Stock underlying the BSB options outstanding immediately prior to the Effective
Time, and shall use its reasonable best efforts to obtain, prior to the
Effective Time, approval for the listing of such NBT Common Stock, subject to
official notice of issuance and BSB shall cooperate with NBT with respect to
such listing.

                           (f)      The information supplied by NBT for
inclusion in the Registration Statement or the Joint Proxy Statement (including
incorporation by reference)


                                       41
<PAGE>   42

shall not, at (i) the time the Registration Statement is declared effective,
(ii) the time the Joint Proxy Statement (or any amendment thereof or supplement
thereto), is first mailed to the stockholders of NBT and BSB, respectively, and
(iii) the time of each of the Stockholders' Meetings, and (iv) the Effective
Time, contain any untrue statement of a material fact or omit to state any
material fact required to be stated therein or necessary in order to make the
statements therein not misleading. If at any time prior to the Effective Time,
any event or circumstance relating to NBT or any NBT Subsidiary, or their
respective officers or directors, should be discovered by NBT that pursuant to
the Securities Act or the Exchange Act should be set forth in an amendment or a
supplement to the Registration Statement or the Joint Proxy Statement, NBT shall
promptly inform BSB. All documents that NBT is responsible for filing with the
SEC in connection with the transactions contemplated herein will comply as to
form and substance in all material aspects with the applicable requirements of
the Securities Act and the rules and regulations promulgated thereunder and the
Exchange Act and the rules and regulations promulgated thereunder.

                           (g)      The information supplied by BSB for
inclusion in the Registration Statement or the Joint Proxy Statement (including
incorporation by reference) shall not, at (i) the time the Registration
Statement is declared effective, (ii) the time the Joint Proxy Statement (or any
amendment thereof or supplement thereto), is first mailed to the stockholders of
NBT and BSB, respectively, and (iii) the time of each of the Stockholders'
Meetings, and (iv) the Effective Time, contain any untrue statement of a
material fact or omit to state any material fact required to be stated therein
or necessary in order to make the statements therein not misleading. If at any
time prior to the Effective Time, any event or circumstance relating to BSB or
any BSB Subsidiary, or their respective officers or directors, should be
discovered by BSB that pursuant to the Securities Act or the Exchange Act should
be set forth in an amendment or a supplement to the Registration Statement or
the Joint Proxy Statement, BSB shall promptly inform NBT. All documents that BSB
is responsible for filing with the SEC in connection with the transactions
contemplated herein will comply as to form and substance in all material
respects with the applicable requirements of the Securities Act and the rules
and regulations promulgated thereunder and the Exchange Act and the rules and
regulations promulgated thereunder.

                  SECTION 5.02.  Meetings of Stockholders.

                           (a)      Each of BSB and NBT shall call and hold a
meeting of its stockholders (collectively, the "Stockholders' Meetings"), as
promptly as practicable for the purpose of voting upon the adoption of this
Agreement, and BSB and NBT shall hold the Stockholders' Meetings as soon as
practicable after the date on which the Registration Statement becomes effective
and will use reasonable best efforts to hold the Stockholders' Meetings on the
same day. Each of BSB and NBT shall use its reasonable best efforts to solicit
from its stockholders proxies in favor of the adoption of this Agreement, and
shall take all other action necessary or advisable to secure the vote(s) of its
stockholders required by the Delaware Law in each case as applicable to obtain
such approvals; provided, however, that BSB or NBT, as applicable, shall not be
obligated to solicit proxies in favor of the adoption of this Agreement at its
Stockholders' Meeting to the extent that the Board of Directors of BSB or NBT,
as applicable, determines in good faith that such failure to solicit proxies is
required in order to comply with its fiduciary duties under


                                       42
<PAGE>   43

applicable Law after receiving advice to such effect from independent legal
counsel (who may be such party's regularly engaged outside legal counsel);
provided further, however, that notwithstanding anything to the contrary in the
foregoing, each of BSB and NBT shall hold its Stockholders' Meeting in
accordance with the time periods specified in the first sentence of this Section
5.02.

                  SECTION 5.03.  Access to Information; Confidentiality.

                           (a)      From the date hereof to the Effective Time,
to the extent permitted by applicable Laws and contracts, BSB will provide to
NBT (and its officers, directors, employees, accountants, consultants, legal
counsel, investment bankers, advisors, agents and other representatives,
collectively, "Representatives") access to all information and documents which
NBT may reasonably request regarding the business, assets, liabilities,
employees, contracts and other aspects of BSB.

                           (b)      From the date hereof to the Effective Time,
to the extent permitted by applicable Law and contracts, NBT will provide to BSB
and its Representatives access to all information and documents which BSB may
reasonably request regarding the business, assets, liabilities, employees,
contracts and other aspects of NBT.

                           (c)      The Parties shall comply with and shall
cause their respective Representatives to comply with, all their respective
obligations under the Confidentiality Agreements entered into by the parties
(the "Confidentiality Agreements"), it being understood that the Parties hereto
shall have the rights as beneficiaries under such agreements.

                           (d)      No investigation pursuant to this Section
5.03 shall affect any representation or warranty in this Agreement of any Party
hereto or any condition to the obligations of the parties hereto.

                  SECTION 5.04.  Appropriate Action; Consents; Filings.

                  BSB and NBT shall use all reasonable efforts to (i) take, or
cause to be taken, all appropriate action, and do, or cause to be done, all
things necessary, proper or advisable under applicable law to consummate and
make effective the transactions contemplated by this Agreement; (ii) obtain all
consents, licenses, permits, waivers, approvals, authorizations or orders
required under Law (including, without limitation, all foreign and domestic
(federal, state and local) governmental and regulatory rulings and approvals and
parties to contracts) in connection with the authorization, execution and
delivery of this Agreement and the consummation by them of the transactions
contemplated hereby and thereby, including, without limitation, the Merger; and
(iii) make all necessary filings, and thereafter make any other required
submissions, with respect to this Agreement and the Merger required under (A)
the Securities Act and the Exchange Act and the rules and regulations
promulgated thereunder, and any other applicable federal or state securities
laws; (B) any applicable federal or state banking laws (including, without
limitation, filing a notice with the FRB with respect to approval of the Merger
under the BHCA and the applicable regulations promulgated thereunder or a
request for waiver of the jurisdiction of the FRB under the BHCA); and (C) any
other applicable law (including, without limitation,


                                       43
<PAGE>   44

any applicable state insurance laws). BSB and NBT shall cooperate with each
other in connection with the making of all such filings, including providing
copies of all such documents to the non-filing party and its advisors prior to
filing. BSB and NBT shall furnish all information required for any application
or other filing to be made pursuant to the rules and regulations of any
applicable law (including all information required to be included in the Joint
Proxy Statement and the Registration Statement) in connection with the
transactions contemplated by this Agreement. In case at any time after the
Effective Time any further action is necessary or desirable to carry out the
purposes of this Agreement, the proper officers and directors of each party to
this Agreement shall use all reasonable efforts to take all such necessary
action. Anything in this Agreement notwithstanding, neither BSB nor NBT shall be
required by virtue of this Agreement to comply with or agree to any regulatory
order, condition, demand, or request that seeks the divestiture of deposits,
branches, or loans whose divestiture would constitute a Material Adverse Effect
with respect to the Surviving Corporation.

                  SECTION 5.05.  No Solicitation of Transactions.

                           (a)      BSB shall immediately cease and cause to be
terminated any existing discussions or negotiations relating to a Competing
Proposal (as defined below), other than with respect to the Merger, with any
parties conducted heretofore. BSB will not, directly or indirectly, and will
instruct its Representatives not to, directly or indirectly, initiate, solicit
or encourage (including by way of furnishing information or assistance), or take
any other action to facilitate, any inquiries or the making of any proposal that
constitutes, or reasonably may be expected to lead to, any Competing Proposal,
or enter into or maintain discussions or negotiate with any person in
furtherance of or relating to such inquiries or to obtain a Competing Proposal,
or agree to or endorse any Competing Proposal, or authorize or permit any
Representative of BSB or any of its subsidiaries to take any such action, and
BSB shall use its reasonable best efforts to cause the Representatives of BSB
and the BSB Subsidiaries not to take any such action, and BSB shall promptly
notify NBT if any such inquiries or proposals are made regarding a Competing
Proposal, and BSB shall keep NBT informed, on a current basis, of the status and
terms of any such proposals; provided, however, that prior to such time as the
stockholders of BSB shall have adopted and approved this Agreement in accordance
with Delaware Law, nothing contained in this Section 5.05 shall prohibit the
Board of Directors of BSB from (i), in connection with a Superior Competing
Transaction (as defined below), furnishing information to, or entering into
discussions or negotiations with, any person that makes an unsolicited bona fide
proposal to acquire BSB pursuant to a merger, consolidation, share exchange,
business combination or other similar transaction, if, and only to the extent
that, (A) the Board of Directors of BSB, after consultation with and based upon
the advice of independent legal counsel, determines in good faith that such
action is required for the Board of Directors of BSB to comply with its
fiduciary duties to stockholders imposed by Delaware Law, (B) prior to
furnishing such information to, or entering into discussions or negotiations
with, such person, BSB provides written notice to NBT to the effect that it is
furnishing information to, or entering into discussions or negotiations with,
such person, (C) prior to furnishing such information to such person, BSB
receives from such person an executed confidentiality agreement with terms no
less favorable to BSB than those contained in the Confidentiality Agreements,
and (D) BSB


                                       44
<PAGE>   45

keeps NBT informed, on a current basis, of the status and details of any such
discussions or negotiations; or (ii) complying with Rule 14e-2 promulgated under
the Exchange Act.

                           (b)      NBT shall immediately cease and cause to be
terminated any existing discussions or negotiations relating to a Competing
Proposal, other than with respect to the Merger, with any parties conducted
heretofore. NBT will not, directly or indirectly, and will instruct its
Representatives not to, directly or indirectly, initiate, solicit or encourage
(including by way of furnishing information or assistance), or take any other
action to facilitate, any inquiries or the making of any proposal that
constitutes, or may reasonably may be expected to lead to, any Competing
Proposal, or enter into or maintain discussions or negotiate with any person in
furtherance of or relating to such inquiries or to obtain a Competing Proposal,
or agree to or endorse any Competing Proposal, or authorize or permit any
Representative of NBT or any of its subsidiaries to take any such action, and
NBT shall use its reasonable best efforts to cause the Representatives of NBT
and the NBT Subsidiaries not to take any such action, and NBT shall promptly
notify BSB if any such inquiries or proposals are made regarding a Competing
Proposal, and NBT shall keep BSB informed, on a current basis, of the status and
terms of any such proposals; provided, however, that prior to such time as the
stockholders of NBT shall have adopted and approved this Agreement in accordance
with Delaware Law, nothing contained in this Section 5.05 shall prohibit the
Board of Directors of NBT from (i) in connection with a Superior Competing
Transaction, furnishing information to, or entering into discussions or
negotiations with, any person that makes an unsolicited bona fide proposal to
acquire NBT pursuant to a merger, consolidation, share exchange, business
combination or other similar transaction, if, and only to the extent that, (A)
the Board of Directors of NBT, after consultation with and based upon the advice
of independent legal counsel, determines in good faith that such action is
required for the Board of Directors of NBT to comply with its fiduciary duties
to stockholders imposed by Delaware Law, (B) prior to furnishing such
information to, or entering into discussions or negotiations with, such person,
NBT provides written notice to BSB to the effect that it is furnishing
information to, or entering into discussions or negotiations with, such person,
(C) prior to furnishing such information to such person, NBT receives from such
person an executed confidentiality agreement with terms no less favorable to NBT
than those contained in the Confidentiality Agreements, and (D) NBT keeps BSB
informed, on a current basis, of the status and details of any such discussions
or negotiations; or (ii) complying with Rule 14e-2 promulgated under the
Exchange Act.

                           (c)      For purposes of this Agreement,
"Competing Proposal" shall mean any of the following involving BSB or any BSB
Subsidiary, on the one hand, or NBT or any NBT Subsidiary, on the other hand:
any inquiry, proposal or offer from any person relating to any direct or
indirect acquisition or purchase by such person of a business of BSB or NBT, as
applicable, that constitutes 15% or more of the net revenues, net income or
assets of BSB or NBT, as applicable, and its subsidiaries, taken as a whole, or
15% or more of any class of equity securities of BSB or NBT, as applicable, or
any of its subsidiaries, any tender offer or exchange offer that if consummated
would result in any person beneficially owning 15% or more of any class of
equity securities of BSB or NBT, as applicable, or any of its subsidiaries, any
merger, consolidation, business combination, recapitalization, liquidation,
dissolution or similar transaction involving BSB or NBT, as applicable, or any
of its subsidiaries, other than the transactions contemplated by this Agreement.


                                       45
<PAGE>   46

                           (d)      For purposes of this Agreement "Superior
Competing Transaction" shall mean any of the following involving BSB or any BSB
Subsidiary, on the one hand, or NBT or any NBT Subsidiary, on the other hand:
any proposal made by a third party to acquire, directly or indirectly, including
pursuant to a tender offer, exchange offer, merger, consolidation, business
combination, recapitalization, liquidation, dissolution or similar transaction,
for consideration consisting of cash and/or securities, more than 50% of the
combined voting power of the shares of BSB Common Stock or NBT Common Stock, as
applicable, then outstanding or all or substantially all the assets of BSB and
NBT, as applicable, and otherwise on terms which the Board of Directors of BSB
or NBT, as applicable, determines in its good faith judgment (based on the
opinion of KBW or MBD, as applicable, or another financial advisor of nationally
recognized reputation) to be more favorable to its stockholders than the Merger
and for which financing, to the extent required, is then committed or which if
not committed is, in the good faith judgment of its Board of Directors,
reasonably capable of being obtained by such third party.

                  SECTION 5.06.  Indemnification.

                           (a)      From and after the Effective Time through
the sixth anniversary thereof, or until the final disposition of such Claim (as
herein defined) with respect to any Claim asserted within the period, NBT and
the Surviving Corporation shall, jointly and severally, indemnify, defend and
hold harmless the present and former officers, directors and employees of BSB
determined as of the Closing Date (collectively, the "Indemnified Parties")
against all losses, expenses, claims, damages, liabilities or amounts that are
paid in settlement of (with the approval of NBT and the Surviving Corporation,
which will not be unreasonably withheld), or in connection with, any claim,
action, suit, proceeding or investigation (a "Claim"), based in whole or in part
on the fact that such person is or was such a director, officer or employee and
arising out of actions or omissions occurring at or prior to the Effective Time
(including the transactions contemplated by this Agreement), in each case to the
fullest extent permitted under Delaware Law and the Federal Deposit Insurance
Act ("FDIA") and NBT's Certificate of Incorporation and Bylaws (and shall pay
expenses in advance of the final disposition of any such action or proceeding to
each Indemnified Party to the fullest extent permitted under Delaware Law and
the FDIA, upon receipt from the Indemnified Party to whom expenses are advanced
of the undertaking to repay such advances; provided that the person to whom
expenses are advanced provides an undertaking to repay such expenses if it is
ultimately determined that such person is not entitled to indemnification).

                           (b)      Any Indemnified Party wishing to claim
indemnification under this Section 5.06, upon learning of any such Claim, shall
notify NBT and the Surviving Corporation (although the failure so to notify NBT
and the Surviving Corporation shall not relieve either thereof from any
liability that NBT or the Surviving Corporation may have under this Section
5.06, except to the extent such failure materially prejudices such party). NBT
and the Surviving Corporation shall have the right to assume the defense thereof
and if such right is exercised NBT and the Surviving Corporation shall not be
liable to such Indemnified Parties for any legal expenses of other counsel or
any other expenses subsequently incurred by such Indemnified Parties in
connection with the defense thereof, except that if NBT and the Surviving
Corporation elect not to assume such defense or there is a conflict of interest
between NBT and the Surviving Corporation and the Indemnified


                                       46
<PAGE>   47

Parties, the Indemnified Parties may retain counsel satisfactory to them, and,
in such case, NBT and the Surviving Corporation shall pay all reasonable fees
and expenses of such counsel for the Indemnified Parties promptly as statements
therefor are received; provided, however, that (i) NBT and the Surviving
Corporation shall not, in connection with any one such action or proceeding or
separate but substantially similar actions or proceedings arising out of the
same general allegations, be liable for the fees and expenses of more than one
separate firm of attorneys at any time for all Indemnified Parties except to the
extent that local counsel, in addition to such parties' regular counsel, is
necessary or desirable in order to effectively defend against such action or
proceeding, (ii) NBT, the Surviving Corporation and the Indemnified Parties will
cooperate in the defense of any such matter, or (iii) NBT and the Surviving
Corporation shall not be liable for any settlement effected without its prior
written consent, which consent will not be unreasonably withheld or delayed, and
provided, further, that the Surviving Corporation shall not have any obligation
hereunder to any Indemnified Party when and if a court of competent jurisdiction
shall ultimately determine, and such determination shall have become final and
not subject to further appeal, that the indemnification of such Indemnified
Party in the manner contemplated hereby is prohibited by applicable law. No
Indemnified Party shall consent to entry of any judgment or enter into any
settlement that does not include as an unconditional term thereof the giving by
the claimant or plaintiff to such Indemnified Party of a release, in form and
substance reasonably satisfactory to such Indemnified Party, from all liability
in respect of such claim or litigation for which such Indemnified Party would be
entitled to indemnification hereunder.

                           (c)      NBT shall purchase for the benefit of the
persons serving as executive officers and directors of BSB immediately prior to
the Effective Time, directors' and officers' liability insurance coverage for
three years after the Effective Time, under either BSB's policy in existence on
the date hereof, or under a policy of similar coverage and amounts containing
terms and conditions which are generally not less advantageous than BSB's
current policy, and in either case, with respect to acts or omissions occurring
prior to the Effective Time which were committed by such executive officers and
directors in their capacity as such provided, however, that in no event shall
NBT be required to expend pursuant to this Section 5.06(c) more than the amount
equal to 150 % of the current annual amount expended by BSB to maintain or
procure insurance coverage pursuant hereto. In connection with the foregoing,
BSB agrees to provide such insurer or substitute insurer with such
representations as such insurer may reasonably request with respect to the
reporting of any prior claims.

                           (d)      This Section 5.06 is intended to be for the
benefit of, and shall be enforceable by, the Indemnified Parties referred to
herein, their heirs and personal representatives and shall be binding on NBT and
the Surviving Corporation and their respective successors and assigns.

                  SECTION 5.07.  Employee Benefits.

                           (a)      If any employee of BSB, any BSB Subsidiary,
NBT or any NBT Subsidiary becomes a participant in any employee benefit plan,
practice, or policy of the Surviving Corporation, the Resulting Bank or any
related entity, such employee shall be given credit under such plan, practice,
or policy for all service prior to the Effective Time


                                       47
<PAGE>   48

with BSB, such BSB Subsidiary, NBT, or such NBT Subsidiary for purposes of
eligibility and vesting, but not for benefit accrual purposes under any such
plan, practice, or policy in which such employee was not a participant before
the Effective Time (except that, if any such employee benefit plan which is
instituted or assumed ("Assumed DB Plan") by the Surviving Corporation, the
Resulting Bank or related entity pursuant to Section 5.07(c) is a defined
benefit plan with a cash balance feature, each such employee shall receive
credit under such Assumed DB Plan for his service with his employer prior to the
Effective Time for benefit accrual purposes, except that the benefit accrual
under any predecessor defined benefit plan in which such employee participated
shall be taken into account under the Assumed DB Plan), for which such service
is taken into account or recognized, and, if necessary, the Surviving
Corporation, the Resulting Bank, or related entity as applicable, shall cause
any and all pre-existing condition limitations and eligibility waiting periods
under group health plans to be waived with respect to such participants and
their eligible dependents (except to the extent such pre-existing condition
limitations are no more onerous than similar limitations, or such waiting
periods do not extend any waiting period, applicable to such employee under the
plans of BSB or any BSB Subsidiary), provided that there be no duplication of
such benefits as are provided under any employee benefit plans, practices, or
policies of BSB, any BSB Subsidiary, NBT or any NBT Subsidiary that are
instituted or continued in effect following the Effective Time.

                           (b)      Each employee of BSB, any BSB Subsidiary,
NBT or any NBT Subsidiary (except any employee who is a party to an employment,
change of control or other agreement providing for severance with BSB or any BSB
Subsidiary) who becomes an employee of the Surviving Corporation, Resulting Bank
or any related entity or who, following the Effective Time, remains an employee
of BSB, any BSB Subsidiary, NBT or any NBT Subsidiary and is terminated by the
Surviving Corporation, the Resulting Bank or any related entity subsequent to
December 31, 2000 shall be entitled to severance pay, if any, in accordance with
the Surviving Corporation's, Resulting Bank's or related entity's new severance
plan developed and instituted pursuant to Section 5.07(c) on or before December
31, 2000. Such employee's service with BSB, such BSB Subsidiary, NBT or such NBT
Subsidiary shall be treated as service with the Surviving Corporation, Resulting
Bank or related entity for purposes of determining the amount of severance pay,
if any, under the new severance plan of the Surviving Corporation, Resulting
Bank or related entity. If any employee is terminated after the Effective Time
but prior to January 1, 2001, such employee shall be covered by his former
employer's severance policy.

                           (c)      On or before January 1, 2001, the Parties
will review their respective Plans, and develop and institute new plans
effective January 1, 2001. The overall benefits program so developed and
instituted for the Surviving Corporation, Resulting Bank and each related
entity, to the extent feasible, shall be comparable to the previous overall
benefit programs of BSB, BSB Bank, NBT and NBT Bank. In order to effect the
foregoing, the Surviving Corporation, Resulting Bank, and related entities, as
applicable, shall, on or before January 1, 2001, adopt any new plan documents,
or amend existing Plan documents (including the Assumed DB Plan referred to in
Section 5.07(a) above) and shall file any form that may be required to comply
with the terms of the resulting Plans, the Code and ERISA. In the event that
employees who were employees of BSB or any BSB Subsidiary at the Effective Time
become participants in a defined benefit plan of the Surviving Corporation,
Resulting Bank or a related entity that has a cash


                                       48
<PAGE>   49

balance feature, the Surviving Corporation will use commercially reasonable
efforts to provide such employees with substantially similar elections with
respect to participation in such plan as were provided to similarly situated
employees of NBT and NBT Bank with respect to such plan. Nothing in this Section
5.07(c) shall be deemed to require any duplication of benefits. Moreover,
nothing in this Agreement shall limit the right and authority of the Surviving
Corporation, the Resulting Bank or related entities after the Effective Time to
adopt, amend, modify or terminate any Plan.

                  SECTION 5.08.  Executive Agreements and Employee Severance.

                           (a)      NBT and BSB agree to cause the Surviving
Corporation and each relevant BSB Subsidiary or NBT Subsidiary to honor, without
modification, and perform its obligations under, the contracts, plans and
arrangements listed in Section 5.08(a) of BSB Disclosure Schedule and the NBT
Disclosure Schedule.

                           (b)      Following the Merger, it is the intent of
NBT and the Surviving Corporation that such entities will, and will cause any of
their respective direct and indirect subsidiaries to, in connection with
reviewing candidates for employment positions, give equal opportunity for such
positions to employees of NBT and any NBT Subsidiaries and employees of BSB and
any BSB Subsidiaries. In addition, employees of BSB will be accorded equal
priority in the hiring process.

                  SECTION 5.09.  Notification of Certain Matters.

                  BSB shall give prompt notice to NBT, and NBT shall give prompt
notice to BSB, of (i) the occurrence, or non-occurrence, of any event the
occurrence, or non-occurrence, of which would be likely to cause any
representation or warranty contained in this Agreement to be untrue or
inaccurate, and (ii) any failure of BSB or NBT, as the case may be, to comply
with or satisfy any covenant, condition, or agreement to be complied with or
satisfied by it hereunder; provided, however, that the delivery of any notice
pursuant to this Section 5.09 shall not limit or otherwise affect the remedies
available hereunder to the Party receiving such notice.

                  SECTION 5.10.  Public Announcements.

                  NBT and BSB shall consult with each other before issuing any
press release or otherwise making any public statements with respect to the
Merger and shall not issue any such press release or make any such public
statement prior to such consultation and with mutual consent of both parties,
except as may be required by law or any listing agreement with the Nasdaq Stock
Market.

                  SECTION 5.11.  Expenses.

                  (a)      All Expenses (as described below) incurred by NBT and
BSB shall be borne by the Party which has incurred the same, except that the
Parties shall share equally in the cost of filing the Registration Statement
with the SEC, printing the Joint Proxy Statement and all other regulatory filing
fees incurred in connection with this Agreement. Except as set forth in the next
sentence, in the event that this Agreement is terminated by either NBT or BSB by
reason of a material breach pursuant to Sections 7.01(c)


                                       49
<PAGE>   50

or (d) hereof or by NBT or BSB pursuant to Sections 7.01(e) and (f) hereof, the
other Party shall pay all documented, reasonable costs and expenses up to
$350,000 incurred by the terminating Party in connection with this Agreement and
the transactions contemplated hereby. In the event that this Agreement is
terminated by NBT or BSB under Section 7.01(e) by reason of stockholders not
having given any required approval, the Party not receiving the required
approval shall pay all documented, reasonable costs and expenses up to $350,000
incurred by the other Party in connection with this Agreement and the
transactions contemplated hereby. In the event that this Agreement is terminated
by NBT or BSB under Section 7.01(g) or (h) by reason of one of the Parties
having agreed to enter into an Superior Competing Transaction other than as
contemplated hereby, the Party entering into the Superior Competing Transaction
shall pay all documented, reasonable costs and expenses up to $350,000 incurred
by the other Party in connection with this Agreement and the transactions
contemplated hereby.

                           (b)      "Expenses" as used in this Agreement shall
include all reasonable out-of-pocket expenses (including, without limitation,
all fees and expenses of counsel, accountants, investment bankers, experts and
consultants to the Party and its affiliates) incurred by a Party or on its
behalf in connection with or related to the authorization, preparation and
execution of this Agreement, BSB Stock Option Agreement and the NBT Stock Option
Agreement, the solicitation of stockholder approvals and all other matters
related to the closing of the transactions contemplated hereby.

                  SECTION 5.12.  Delivery of Stockholder List.

                  BSB shall arrange to have its transfer agent deliver to NBT or
its designee, from time to time prior to the Effective Time, a true and complete
list setting forth the names and addresses of the stockholders of BSB, their
holdings of stock as of the latest practicable date, and such other stockholder
information as NBT may reasonably request.

                  SECTION 5.13.  Letters of Accountants.

                           (a)      BSB shall use its reasonable efforts to
cause to be delivered to NBT a "comfort" letter of PricewaterhouseCoopers LLP,
BSB's independent public accountants, dated and delivered on the date on which
the Registration Statement shall become effective and as the date of the
Effective Time, and addressed to NBT, in the form, scope and content
contemplated by Statement on Auditing Standards No. 72 issued by the American
Institute of Certified Public Accountants, Inc. ("SAS 72"), relating to the
financial statements and other financial data with respect to BSB and its
consolidated subsidiaries included or incorporated by reference in the Joint
Proxy Statement and such other matters as may be reasonably required by NBT, and
based upon procedures carried out to a specified date not earlier than five days
prior to the date thereof.

                           (b)      NBT shall use its reasonable efforts to
cause to be delivered to BSB a "comfort" letter of KPMG LLP, NBT's independent
public accountants, dated and delivered on the date on which the Registration
Statement shall become effective and as of the date of the Effective Time, and
addressed to BSB, in the form, scope and content contemplated by SAS 72,
relating to the financial statements and other financial data with respect to
NBT and its consolidated subsidiaries included in or incorporated by reference
in the Joint Proxy Statement and such other matters as may be reasonably
required by BSB,


                                       50
<PAGE>   51

and based upon procedures carried out to a specified date not earlier than five
days prior to the date thereof.

                  SECTION 5.14.  BSB Reports.

                           (a)      BSB shall timely file all required BSB
Reports, each of which (i) shall be prepared in all material respects in
accordance with, in the case of filings with the SEC, the requirements of the
Securities Act and the Exchange Act and the rules and regulations of the SEC
promulgated thereunder, and in the case of all other BSB Reports, the
requirements of any Regulatory Agency applicable to such BSB Reports and (ii)
shall not at the time they are filed contain any untrue statement of a material
fact or omit to state a material fact required to be stated therein or necessary
in order to make the statements therein, in the light of the circumstances under
which they were made, not misleading.

                           (b)      Each of the consolidated financial
statements (including, in each case, any notes thereto) contained in BSB SEC
Reports filed after the date of this Agreement and prior to the Effective Time
shall be prepared in accordance with the published rules and regulations of the
SEC and GAAP throughout the periods indicated and each shall present fairly, in
all material respects, the consolidated financial position, results of
operations and cash flows of BSB and its consolidated subsidiaries at the
respective dates thereof and for the respective periods indicated therein
(subject, in the case of unaudited statements, to normal and recurring year-end
adjustments which are not expected, individually or in the aggregate, to have a
Material Adverse Effect upon BSB).

                  SECTION 5.15.  NBT Reports.

                           (a)      NBT shall timely file all required NBT
Reports, each of which (i) shall be prepared in all material respects in
accordance with, in the case of filings with the SEC, the requirements of the
Securities Act and the Exchange Act and the rules and regulations of the SEC
promulgated thereunder, and in the case of all other NBT Reports, the
requirements of any Regulatory Agency applicable to such NBT Reports and (ii)
shall not at the time they are filed contain any untrue statement of a material
fact or omit to state a material fact required to be stated therein or necessary
in order to make the statements therein, in the light of the circumstances under
which they were made, not misleading.

                           (b)      Each of the consolidated financial
statements (including, in each case, any notes thereto) contained in the NBT SEC
Reports filed after the date of this Agreement and prior to the Effective Time
shall be prepared in accordance with the published rules and regulations of the
SEC and GAAP throughout the periods indicated and each shall present fairly, in
all material respects, the consolidated financial position, results of
operations and cash flows of NBT and its consolidated subsidiaries as at the
respective dates thereof and for the respective periods indicated therein
(subject, in the case of unaudited statements, to normal and recurring year-end
adjustments which are not expected, individually or in the aggregate, to have a
Material Adverse Effect upon NBT).


                                       51
<PAGE>   52

                  SECTION 5.16.  Pooling.

                  NBT and BSB shall take all reasonable actions to insure
pooling of interest treatment for the Merger.

                  SECTION 5.17.  Disclosure Schedules

                  NBT and BSB shall promptly advise the other party of any
change or event that, individually or in the aggregate, has or would be
reasonably likely to have a Material Adverse Effect on NBT or BSB, as the case
may be, or to cause or constitute a breach of any of its representations,
warranties or covenants contained herein. From time to time prior to the Closing
Date, each party will promptly supplement or amend its disclosure schedule
delivered in connection with the execution of this Agreement to reflect any
matter which, if existing, occurring or known at the date of this Agreement,
would have been required to be set forth or described in such disclosure
schedule or which is necessary to correct any information in such disclosure
schedule which has been rendered inaccurate thereby. No supplement or amendment
to such disclosure schedule shall have any effect for the purpose of determining
satisfaction of the conditions set forth in Articles II or III hereof, as the
case may be, or the compliance by NBT or BSB, as the case may be, with the
respective covenants set forth in Article IV hereof.

                  SECTION 5.18.  Regulatory Matters.

                  (a)      As promptly as practicable following the execution
and delivery of this Agreement, if applicable, BSB and NBT will prepare and file
with the United States Federal Trade Commission (the "FTC") and the Antitrust
Division of the United States Department of Justice (the "DOJ") Notification and
Report Forms relating to the transactions contemplated herein if and as required
by the HSR Act, as well as comparable pre-merger notification forms required by
the merger notification or control laws and regulations of any applicable
jurisdiction, as agreed by the parties (the "Antitrust Filings"). The Parties
will comply with any requests for additional information relating to the
Antitrust Filings and will use their reasonable best efforts to secure all
required approvals of the Antitrust Filings.

                  (b)      The Parties hereto shall cooperate with each other
and use their reasonable best efforts to promptly prepare and file all necessary
documentation, to effect all applications, notices, petitions and filings (which
shall include the Antitrust Filings), and to obtain as promptly as practicable
all permits, consents, approvals and authorizations of all third parties and
Governmental Entities which are necessary or advisable to consummate the
transactions contemplated by this Agreement (including without limitation the
Merger). BSB and NBT shall have the right to review in advance, and to the
extent practicable each will consult the other on, in each case subject to
applicable laws relating to the exchange of information, all the information
relating to BSB and NBT, as the case may be, which appears in any filing made
with, or written materials submitted to, any third party or any Governmental
Entity in connection with the transactions contemplated by this Agreement and
will promptly notify each other of any communication with any Governmental
Entity and provide the other with an opportunity to participate in any meetings
with a Governmental Entity relating thereto; provided, however, that nothing
contained herein shall be deemed to provide either Party with a right to review
any information provided to any Governmental Entity on a confidential basis in
connection with the transactions contemplated hereby. In


                                       52
<PAGE>   53

exercising the foregoing right, each of the Parties hereto shall act reasonably
and as promptly as practicable. The Parties hereto agree that they will consult
with each other with respect to the obtaining of all permits, consents,
approvals and authorizations of all third parties and Governmental Entities
necessary or advisable to consummate the transactions contemplated by this
Agreement and each Party will keep the other apprised of the status of matters
relating to contemplation of the transactions contemplated herein.

                  (c)      BSB and NBT shall promptly advise each other upon
receiving any communication from any Governmental Entity whose consent or
approval is required for consummation of the transactions contemplated by this
Agreement which causes such party to believe that there is a reasonable
likelihood that any requisite regulatory approval will not be obtained or that
the receipt of any such approval will be materially delayed.

                                   ARTICLE VI

                              CONDITIONS OF MERGER

                  SECTION 6.01.  Conditions to Obligation of Each Party to
                  Effect the Merger.

                  The respective obligations of each Party to effect the Merger
shall be subject to the satisfaction at or prior to the Effective Time of the
following conditions:

                           (a)      Effectiveness of the Registration Statement.
The Registration Statement shall have been declared effective by the SEC under
the Securities Act. No stop order suspending the effectiveness of the
Registration Statement shall have been issued by the SEC and no proceedings for
that purpose shall, on or prior to the Effective Time, have been initiated or,
to the knowledge of NBT or BSB, threatened by the SEC. NBT shall have received
all other federal or state securities permits and other authorizations necessary
to issue NBT Common Stock in exchange for BSB Common Stock and to consummate the
Merger.

                           (b)      Stockholder Approvals. This Agreement shall
have been approved and adopted by the requisite vote of the stockholders of BSB.
The Agreement and the issuance of shares of NBT Common Stock in the Merger
pursuant to this Agreement and the amendments to NBT's Certificate of
Incorporation to increase the number of shares of NBT Common Stock that NBT is
authorized to issue and to provide a new name for the Surviving Corporation
shall have been approved by the requisite vote of the stockholders of NBT.

                           (c)      Regulatory Approvals. All requisite
approvals of this Agreement and the transactions contemplated hereby shall have
been received from the FRB and any other applicable regulatory authority, and
all conditions required to be satisfied prior to the Effective Time imposed by
the terms of such approvals shall have been satisfied and all waiting periods
relating to such approvals shall have expired.

                           (d)       Nasdaq Listing. The shares of NBT Common
Stock that are to be issued to the stockholders of BSB and holders of BSB
options in the Merger shall have


                                       53
<PAGE>   54

been authorized for listing on the Nasdaq Stock Market's National Market,
subject to notice of issuance.

                           (e)      No Order. No federal or state governmental
or regulatory authority or other agency or commission, or federal or state court
of competent jurisdiction, shall have enacted, issued, promulgated, enforced or
entered any statute, rule, regulation, executive order, decree, injunction or
other order (whether temporary, preliminary or permanent) which is in effect
restricting, preventing or prohibiting consummation of the transactions
contemplated by this Agreement.

                           (f)      No Challenge. There shall not be pending any
action, proceeding or investigation before any court or administrative agency or
by any government agency or any other person (i) challenging or seeking material
damages in connection with the Merger or (ii) seeking to restrain, prohibit or
limit the exercise of full rights of ownership or operation by NBT or the NBT
Subsidiaries of all or any portion of the business or assets of BSB or any BSB
Subsidiary, which in either case has or would have a Material Adverse Effect on
NBT and the Surviving Corporation taken as a whole.

                           (g)      Pooling Opinions. NBT and BSB shall have
received an opinion from KPMG LLP and PriceWaterhouseCoopers LLP, respectively,
to the effect that the Merger qualifies for pooling of interests accounting
treatment if consummated in accordance with this Agreement.

                           (h)      NBT Tax Opinion. NBT and BSB shall have
received an opinion of Duane, Morris & Heckscher LLP, special counsel for NBT
dated the Closing Date (as defined in Section 8.01), based upon appropriate
assumptions and qualifications, to the effect that the Merger and the Bank
Merger will each be treated under existing law for federal income tax purposes
as a reorganization within the meaning of Section 368(a) of the Code, and that
NBT and BSB will each be a party to that reorganization within the meaning of
Section 368(b) of the Code that shall have been delivered and that shall not
have been withdrawn or modified. In such opinion, special counsel for NBT shall
be entitled to rely upon representations of NBT, BSB and any other party
reasonably satisfactory in form and substance to such counsel.

                  SECTION 6.02.  Additional Conditions to Obligations of NBT.

                  The obligation of NBT to effect the Merger is also subject to
the following conditions:

                           (a)      Representation and Warranties. Each of the
representations and warranties of BSB set forth in this Agreement shall be true
and correct in all material respects as of the Closing Date (except to the
extent such representations and warranties speak only as of an earlier date, in
which case such representations and warranties shall be true and correct in all
material respects as of such date) as though made as of the Closing Date;
provided, however, that for purposes of this paragraph, such representations and
warranties shall be deemed true and correct in all material respects unless the
failure or failures of such representations and warranties to be so true and
correct, individually or in the aggregate, would have a Material Adverse Effect
on BSB. Such determination of aggregate Material Adverse Effect shall be made as
if there were no materiality


                                       54
<PAGE>   55

qualifications in such representations and warranties. NBT shall have received a
certificate of the Chief Executive Officer of BSB dated the Closing Date to that
effect.

                           (b)      Agreements and Covenants. BSB shall have
performed or complied in all material respects with all obligations required to
be performed by it under this Agreement on or prior to the Effective Time. NBT
shall have received a certificate of the Chief Executive Officer of BSB dated
the Closing Date to that effect.

                           (c)      Consents Obtained. All consents, waivers,
approvals, authorizations or orders required to be obtained, and all filings
required to be made by BSB for the authorization, execution and delivery of this
Agreement and the consummation by it of the transactions contemplated hereby
shall have been obtained and made by BSB, except when the failure to obtain or
make the same, individually or in the aggregate, would not have a Material
Adverse Effect on BSB and BSB Subsidiaries, taken as a whole, or the NBT and the
NBT Subsidiaries, taken as a whole.

                           (d)      Reserves and Accruals. The reserves and
accruals described in Section 4.01(b) shall have been established.

                  SECTION 6.03.  Additional Conditions to Obligations of BSB.

                  The obligation of BSB to effect the Merger is also subject to
the following conditions:

                           (a)      Representations and Warranties. Each of the
representations and warranties of NBT set forth in this Agreement shall be true
and correct in all material respects as of the Closing Date (except to the
extent such representation and warranties speak as of an earlier date, in which
case such representation and warranties shall be true and correct in all
material respects as of such earlier date) as though made as of the Closing
Date; provided, however, that for purposes of this paragraph, such
representations and warranties shall be deemed true and correct in all material
respects unless the failure or failures of such representations and warranties
to be so true and correct, individually or in the aggregate, would have a
Material Adverse Effect on NBT. Such determination of aggregate Material Adverse
Effect shall be made as if there were no materiality qualifications in such
representations and warranties. BSB shall have received a certificate of the
Chief Executive Officer of NBT dated the Closing Date to that effect.

                           (b)      Agreements and Covenants. NBT shall have
performed or complied in all material respects with all obligations required to
be performed by it under this Agreement on or prior to the Effective Time. BSB
shall have received a certificate of the Chief Executive Officer of NBT dated
the Closing Date to that effect.

                           (c)      Consents Obtained. All consents, waivers,
approvals, authorizations or orders required to be obtained, and all filings
required to be made by NBT for the authorization, execution and delivery of this
Agreement and the consummation by it of the transactions contemplated hereby
shall have been obtained and made by NBT, except when the failure to obtain or
make the same, individually or in the aggregate, would not have a Material
Adverse Effect on BSB and BSB Subsidiaries, taken as a whole, or the NBT and the
NBT Subsidiaries, taken as a whole.


                                       55
<PAGE>   56

                                   ARTICLE VII

                        TERMINATION, AMENDMENT AND WAIVER

                  SECTION 7.01.  Termination.

                  This Agreement may be terminated at any time prior to the
Effective Time, whether before or after approval by the stockholders of BSB and
NBT of the matters presented in connection with the Merger:

                           (a)      by mutual written consent duly authorized by
the Boards of Directors of each of NBT and BSB;

                           (b)      by either NBT or BSB if either (i) the
Effective Time shall not have occurred on or before November 30, 2000; provided,
however, that the right to terminate this Agreement under this Section 7.01(b)
shall not be available to any Party whose failure to fulfill any obligation
under this Agreement has been the cause of, or resulted in, the failure of the
Effective Time to occur on or before such date or (ii) any injunction preventing
the consummation of the Merger shall have become final and nonappealable;

                           (c)      by NBT, if there has been a breach of any
material representation, warranty, covenant or agreement on the part of BSB set
forth in this Agreement, or if any representation or warranty of BSB shall have
become untrue, in either case such that the conditions set forth in Section
6.02(a) or Section 6.02(b) would not be satisfied and such breach is not cured
within 30 days after written notice thereof to BSB by NBT;

                           (d)      by BSB, if there has been a breach of any
material representation, warranty, covenant or agreement on the part of NBT set
forth in this Agreement, or if any representation or warranty of NBT shall have
become untrue, in either case such that the conditions set forth in Section
6.03(a) or Section 6.03(b) would not be satisfied and such breach is not cured
within 30 days after written notice thereof to NBT by BSB;

                           (e)      by either NBT or BSB if (i) at a duly called
and held stockholders' meeting therefor, this Agreement shall fail to receive
the requisite vote for approval and adoption by BSB's stockholders, or (ii) at a
duly called and held stockholders' meeting therefor, this Agreement and the
issuance of shares of NBT Common Stock in connection with the Merger pursuant to
this Agreement shall fail to receive the requisite vote for approval and
adoption by NBT's stockholders;

                           (f)      by either NBT or BSB, if at a duly called
and held stockholders' meeting therefor, the amendments of NBT's Certificate of
Incorporation to increase the number of shares of NBT Common Stock that NBT is
authorized to issue and to provide a new name for the Surviving Corporation in
connection with the Merger pursuant to this Agreement shall fail to receive the
requisite vote for approval by NBT's stockholders;


                                       56
<PAGE>   57

                           (g)      by BSB, if (i) the Board of Directors of BSB
authorizes BSB, subject to complying with the terms of this Agreement, to enter
into a binding written agreement concerning a transaction that constitutes a
Superior Competing Transaction and the BSB notifies NBT in writing that it
intends to enter into such an agreement, attaching the most current version of
such agreement (or a description of all material terms and conditions thereof)
to such notice, (ii) NBT does not make, within three business days of receipt of
BSB's written notification of its intention to enter into a binding agreement
for a Superior Competing Transaction, an offer that the Board of Directors of
BSB determines, in good faith after consultation with its financial advisors, is
at least as favorable to the stockholders of BSB as the Superior Competing
Transaction, it being understood that BSB shall not enter into any such binding
agreement during such three day period and (iii) BSB prior to such termination
pursuant to this Section 7.01(g) pays to NBT in immediately available funds the
fees required to be paid pursuant to Section 5.11. BSB agrees to notify NBT
promptly if its intention to enter into a written agreement referred to in its
notification shall change at any time after giving such notification; or

                            (h)     by NBT, if (i) the Board of Directors of NBT
authorizes NBT, subject to complying with the terms of this Agreement, to enter
into a binding written agreement concerning a transaction that constitutes a
Superior Competing Transaction and NBT notifies BSB in writing that it intends
to enter into such an agreement, attaching the most current version of such
agreement (or a description of all material terms and conditions thereof) to
such notice, (ii) BSB does not make, within three business days of receipt of
NBT's written notification of its intention to enter into a binding agreement
for a Superior Competing Transaction, an offer that the Board of Directors of
NBT determines, in good faith after consultation with its financial advisors, is
at least as favorable to the stockholders of NBT as the Superior Competing
Transaction, it being understood that NBT shall not enter into any such binding
agreement during such three day period and (iii) NBT prior to such termination
pursuant to this Section 7.01(h) pays to BSB in immediately available funds the
fees required to be paid pursuant to Section 5.11. NBT agrees to notify BSB
promptly if its intention to enter into a written agreement referred to in its
notification shall change at any time after giving such notification.

                  SECTION 7.02.  Effect of Termination.

                  Except as provided in Section 8.02, in the event of
termination of this Agreement pursuant to Section 7.01, this Agreement shall
forthwith become void, there shall be no liability under this Agreement on the
part of NBT or BSB or any of their respective officers or directors and all
rights and obligations of each Party hereto shall cease; provided that
notwithstanding anything to the contrary in this Agreement, none of NBT or BSB
shall be released from any liabilities or damages arising out of its willful
breach of any provision of this Agreement.

                  SECTION 7.03.  Amendment.

                  This Agreement may be amended by the Parties hereto by action
taken by or on behalf of their respective Boards of Directors at any time prior
to the Effective Time; provided, however, that, after approval of this Agreement
by the stockholders of BSB and NBT, no amendment may be made which would (i)
alter or change the amount or kind of


                                       57
<PAGE>   58

consideration into which each Share shall be converted pursuant to this
Agreement upon consummation of the Merger, (ii) alter or change any term of the
certificate of incorporation of the Surviving Corporation to be effected by the
Merger or (iii) alter or change any of the terms or conditions of this Agreement
if such alteration or change would adversely affect the holders of BSB Common
Stock or NBT Common Stock. This Agreement may not be amended except by an
instrument in writing signed by the Parties hereto.

                  SECTION 7.04.  Waiver.

                  At any time prior to the Effective Time, any Party hereto may
(a) extend the time for the performance of any of the obligations or other acts
of the other Party hereto, (b) waive any inaccuracies in the representations and
warranties contained herein or in any document delivered pursuant hereto and (c)
waive compliance with any of the agreements or conditions contained herein. Any
such extension or waiver shall be valid if set forth in an instrument in writing
signed by the Party or Parties to be bound thereby.

                                  ARTICLE VIII

                               GENERAL PROVISIONS

                  SECTION 8.01.  Closing.

                  Subject to the terms and conditions of this Agreement, the
closing (the "Closing") of the Merger will take place at 10:00 a.m. on a date
and place specified by the Parties, which shall be no later than three business
days after the satisfaction or waiver (subject to applicable law) of the latest
to occur of the conditions set forth in Article VI unless extended by mutual
agreement of the Parties (the "Closing Date").

                  SECTION 8.02.  Non-Survival of Representations, Warranties and
                                  Agreements.

                  The representations, warranties and agreements in this
Agreement shall terminate at the Effective Time or upon the termination of this
Agreement pursuant to Article VII, except that the agreements set forth in
Article I shall survive the Effective Time indefinitely and those set forth in
Sections 5.03(c), 5.06, 5.07, 5.08, 5.11, 7.02 and Article VIII hereof shall
survive termination indefinitely.

                  SECTION 8.03.  Notices.

                  All notices and other communications given or made pursuant
hereto shall be in writing and shall be deemed to have been duly given or made
as of the date delivered or mailed if delivered personally or mailed by
registered or certified or overnight mail (postage prepaid, return receipt
requested) to the Parties at the following addresses (or such other address for
a Party as shall be specified by like changes of address) and shall be effective
upon receipt:


                                       58
<PAGE>   59

                  (a)      If to NBT:

                           NBT Bancorp Inc.
                           52 South Broad Street
                           Norwich, New York  13815
                           Attention:  Mr. Daryl R. Forsythe

                           With a copy (which shall not constitute notice) to:

                           Duane, Morris & Heckscher LLP
                           1667 K Street, N.W., Suite 700
                           Washington, D.C.  20006
                           Attention:  Brian D. Alprin, Esq.

                  (b)      If to BSB:

                           BSB Bancorp, Inc.
                           58-68 Exchange Street
                           Binghamton, NY  13902
                           Attention:  President and Chief Executive Officer

                  With a copy (which shall not constitute notice) to:

                           Hogan & Hartson, L.L.P.
                           555 13th Street, N.W.
                           Washington, D.C.  20004
                           Attention:  Stuart G. Stein, Esq.

                           SECTION 8.04.  Additional Definitions.

                  For purposes of this Agreement, the term:

                           (a)      "beneficial owner" with respect to any
Shares, means a person who shall be deemed to be the beneficial owner of such
Shares (i) which such person or any of its affiliates or associates beneficially
owns, directly or indirectly, (ii) which person or any of its affiliates or
associates (as such term is defined in Rule 12b-2 of the Exchange Act) has,
directly or indirectly, (A) the right to acquire (whether such right is
exercisable immediately or subject only to the passage of time), pursuant to any
agreement, arrangement or understanding or upon the exercise of consideration
rights, exchange rights, warrants or options, or otherwise, or (B) the right to
vote pursuant to any agreement, arrangement or understanding, (iii) which are
beneficially owned, directly or indirectly, by any other persons with whom such
person or any of its affiliates or associates has any agreement, arrangement or
understanding for the purpose of acquiring, holding, voting or disposing of any
Shares, or (iv) pursuant to Section 13(d) of the Exchange Act and any rules or
regulations promulgated thereunder;

                           (b)      "Business Day" means any day other than a
day on which banks in New York are required or authorized to be closed;


                                       59
<PAGE>   60

                           (c)      "control" (including the terms "controlled
by" and "under common control with") means the possession, directly or
indirectly or as trustee or executor, of the power to direct or cause the
direction of the management or policies of a person, whether through the
ownership of stock or as trustee or executor, by contract or credit arrangement
or otherwise;

                           (d)      "Material Adverse Effect" means any adverse
change, effect, circumstance, event or condition that is or is reasonably likely
to be materially adverse to NBT or BSB, as the case may be, and their respective
subsidiaries taken as a whole, business, results of operations, properties,
financial condition, individually or in the aggregate, or the ability of such
Party to consummate the transactions contemplated by this Agreement, except that
a Material Adverse Effect shall not be deemed to have occurred as a result of
any change, effect, circumstance, event or condition resulting from (i) general
changes in economic conditions or the securities markets in general; (ii)
general changes in the banking/financial institutions industry; (iii) the Merger
or the transactions contemplated thereby (except that the first $10 million of
reserves and accruals described in Section 4.01(b) shall be excepted from this
definition of "Material Adverse Effect") or the announcement thereof; and (iv) a
change in the trading prices of either NBT's or BSB's equity securities between
the date of the Agreement and the Effective Time of the Merger.

                           (e)      "person" means an individual, corporation,
partnership, association, trust, unincorporated organization, other entity or
group (as defined in Section 13(d) of the Exchange Act).

                  SECTION 8.05.  Headings.

                  The headings contained in this Agreement are for reference
purposes only and shall not affect in any way the meaning or interpretation of
this Agreement.

                  SECTION 8.06.  Severability.

                  If any term or other provision of this Agreement is invalid,
illegal or incapable of being enforced by any rule of law or public policy, all
other conditions and provisions of this Agreement shall nevertheless remain in
full force and effect so long as the economic or legal substance of the
transactions contemplated hereby is not affected in any manner adverse to any
Party. Upon such determination that any term or other provision is invalid,
illegal or incapable of being enforced, the Parties hereto shall negotiate in
good faith to modify this Agreement so as to effect the original intent of the
Parties as closely as possible in an acceptable manner to the end that
transactions contemplated hereby are fulfilled to the extent possible.

                  SECTION 8.07.  Entire Agreement.

                  This Agreement, together with the BSB and NBT Disclosure
Schedules and the Exhibits hereto, constitutes the entire agreement of the
Parties and supersedes all prior agreements and undertakings, both written and
oral, between the Parties, or any of them, with respect to the subject matter
hereof and, except as otherwise expressly provided herein, is not intended to
confer upon any other person any rights or remedies hereunder.


                                       60
<PAGE>   61

                  SECTION 8.08.  Assignment.

                  This Agreement shall not be assigned by operation of law or
otherwise.

                  SECTION 8.09.  Parties in Interest.

                  This Agreement shall be binding upon and inure solely to the
benefit of each Party hereto, and nothing in this Agreement, express or implied,
is intended to or shall confer upon any other person any right, benefit or
remedy of any nature whatsoever under of by reason of this Agreement.

                  SECTION 8.10.  Governing Law.

                  This Agreement shall be governed by, and construed in
accordance with, the laws of the State of Delaware, regardless of the laws that
might otherwise govern under applicable principles of conflicts of law.

                  SECTION 8.11.  Counterparts.

                  This Agreement may be executed in one or more counterparts,
and by the different Parties hereto in separate counterparts, each of which when
executed shall be deemed to be an original but all of which taken together shall
constitute one and the same agreement.


                                       61
<PAGE>   62


                  IN WITNESS WHEREOF, NBT and BSB have caused this Agreement to
be executed as of the date first written above by their respective officers
thereunto duly authorized.

                                  NBT BANCORP INC.

                                  By:      /s/ Daryl R. Forsythe
                                           ---------------------
                                  Name:    Daryl R. Forsythe
                                  Title:   President and Chief Executive Officer

                                  BSB BANCORP, INC.

                                  By:      /s/ Thomas L. Thorn
                                           -------------------
                                  Name:    Thomas L. Thorn
                                  Title:   Acting President and Chief Executive
                                           Officer



                                       62
<PAGE>   63

                          AGREEMENT AND PLAN OF MERGER

                                 BY AND BETWEEN

                                NBT BANCORP INC.

                                       AND

                                BSB BANCORP, INC.

                           DATED AS OF APRIL 19, 2000


<PAGE>   64

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                    Page
                                                                                                    ----
<S>                                                                                                <C>
ARTICLE I  THE MERGER...............................................................................2

      SECTION 1.01.  The Merger.....................................................................2
      SECTION 1.02.  Effective Time.................................................................2
      SECTION 1.03.  Effect of the Merger...........................................................2
      SECTION 1.04.  Certificate of Incorporation and Bylaws........................................3
      SECTION 1.05.  Senior Executive Officers......................................................3
      SECTION 1.06.  Representation on the Board of the Surviving Corporation.......................3
      SECTION 1.07   Composition of the Board of the Resulting Bank.................................5
      SECTION 1.08.  Conversion of Common Stock.....................................................5
      SECTION 1.09.  Exchange of Certificates.......................................................6
      SECTION 1.10.  Treatment of Stock Options.....................................................8
      SECTION 1.11.  Stock Transfer Books...........................................................9
      SECTION 1.12.  Anti-Dilution Adjustment......................................................10
      SECTION 1.13.  Tax Consequences..............................................................10

ARTICLE II  REPRESENTATIONS AND WARRANTIES OF BSB..................................................10

      SECTION 2.01.  Organization and Qualification of BSB; Subsidiaries...........................10
      SECTION 2.02.  Certificate of Incorporation and Bylaws.......................................12
      SECTION 2.03.  Capitalization................................................................12
      SECTION 2.04.  Authority; State Takeover Laws; Certificate of Incorporation..................12
      SECTION 2.05.  No Conflict; Required Filings and Consents....................................13
      SECTION 2.06.  Compliance....................................................................14
      SECTION 2.07.  Securities and Banking Reports; Financial Statements..........................15
      SECTION 2.08.  Absence of Certain Changes or Events..........................................16
      SECTION 2.09.  Absence of Litigation and Agreements..........................................16
      SECTION 2.10.  Employee Benefit Plans........................................................17
      SECTION 2.11.  Material Contracts............................................................19
      SECTION 2.12.  Environmental Matters.........................................................20
      SECTION 2.13.  Taxes.........................................................................21
      SECTION 2.14.  Affiliates....................................................................23
      SECTION 2.15.  Derivative Instruments........................................................23
      SECTION 2.16.  Regulatory Approvals..........................................................23
      SECTION 2.17.  Brokers.......................................................................23
      SECTION 2.18.  Pooling of Interests and Tax Matters..........................................23
      SECTION 2.19.  Vote Required.................................................................24
      SECTION 2.20.  Fairness Opinion..............................................................24
      SECTION 2.21   Rights Agreement..............................................................24
</TABLE>


                                       i
<PAGE>   65

<TABLE>
<S>                                                                                                <C>
ARTICLE III  REPRESENTATIONS AND WARRANTIES OF NBT.................................................24

      SECTION 3.01.  Organization and Qualification of NBT; Subsidiaries...........................24
      SECTION 3.02.  Certificate of Incorporation and Bylaws.......................................26
      SECTION 3.03.  Capitalization................................................................26
      SECTION 3.04.  Authority.....................................................................27
      SECTION 3.05.  No Conflict; Required Filings and Consents....................................27
      SECTION 3.06.  Compliance....................................................................29
      SECTION 3.07.  Securities and Banking Reports; Financial Statements..........................29
      SECTION 3.08.  Absence of Certain Changes or Events..........................................30
      SECTION 3.09.  Absence of Litigation and Agreements..........................................30
      SECTION 3.10.  Employee Benefit Plans........................................................31
      SECTION 3.11.  Material Contracts............................................................33
      SECTION 3.12.  Environmental Matters.........................................................34
      SECTION 3.13.  Taxes.........................................................................35
      SECTION 3.14.  Affiliates....................................................................35
      SECTION 3.15.  Derivative Instruments........................................................36
      SECTION 3.16.  Regulatory Approvals..........................................................36
      SECTION 3.17.  Brokers.......................................................................36
      SECTION 3.18.  Pooling of Interest and Tax Matters...........................................36
      SECTION 3.19.  Votes Required................................................................37
      SECTION 3.20.  Fairness Opinion..............................................................37
      SECTION 3.21   Rights Agreement..............................................................37

ARTICLE IV  COVENANTS OF BSB AND NBT...............................................................37

      SECTION 4.01.  Affirmative Covenants.........................................................37
      SECTION 4.02.  Negative Covenants............................................................38

ARTICLE V  ADDITIONAL AGREEMENTS...................................................................40

      SECTION 5.01.  Registration Statement; Joint Proxy Statement.................................40
      SECTION 5.02.  Meetings of Shareholders......................................................42
      SECTION 5.03.  Access to Information; Confidentiality........................................43
      SECTION 5.04.  Appropriate Action; Consents; Filings.........................................43
      SECTION 5.05.  No Solicitation of Transactions...............................................44
      SECTION 5.06.  Indemnification...............................................................46
      SECTION 5.07.  Employee Benefits.............................................................47
      SECTION 5.08.  Executive Agreements and Employee Severance...................................49
      SECTION 5.09.  Notification of Certain Matters...............................................49
      SECTION 5.10.  Public Announcements..........................................................49
      SECTION 5.11.  Expenses......................................................................49
      SECTION 5.12.  Delivery of Stockolder List...................................................50
      SECTION 5.13.  Letters of Accountants........................................................50
      SECTION 5.14.  BSB Reports...................................................................51
</TABLE>


                                       ii
<PAGE>   66

<TABLE>
<S>                                                                                                              <C>
      SECTION 5.15.  NBT Reports.................................................................................51
      SECTION 5.16.  Pooling.....................................................................................52
      SECTION 5.17   Disclosure Schedules........................................................................52
      SECTION 5.18.  Regulatory Matters..........................................................................52

ARTICLE VI  CONDITIONS OF MERGER.................................................................................53

      SECTION 6.01.  Conditions to Obligation of Each Party to Effect the Merger.................................53
      SECTION 6.02.  Additional Conditions to Obligations of NBT.................................................54
      SECTION 6.03.  Additional Conditions to Obligations of BSB.................................................55

ARTICLE VII  TERMINATION, AMENDMENT AND WAIVER...................................................................56

      SECTION 7.01.  Termination.................................................................................56
      SECTION 7.02.  Effect of Termination.......................................................................57
      SECTION 7.03.  Amendment...................................................................................57
      SECTION 7.04.  Waiver......................................................................................58

ARTICLE VIII  GENERAL PROVISIONS.................................................................................58

      SECTION 8.01.  Closing.....................................................................................58
      SECTION 8.02.  Non-Survival of Representations, Warranties and
                     Agreements..................................................................................58
      SECTION 8.03.  Notices.....................................................................................58
      SECTION 8.04.  Additional Definitions......................................................................59
      SECTION 8.05.  Headings....................................................................................60
      SECTION 8.06.  Severability................................................................................60
      SECTION 8.07.  Entire Agreement............................................................................60
      SECTION 8.08.  Assignment..................................................................................61
      SECTION 8.09.  Parties in Interest.........................................................................61
      SECTION 8.10.  Governing Law...............................................................................61
      SECTION 8.11.  Counterparts................................................................................61
</TABLE>

EXHIBITS

A        BANK PLAN OF MERGER
B        BSB STOCK OPTION AGREEMENT
C        NBT STOCK OPTION AGREEMENT
D        CERTIFICATE OF MERGER
E        SENIOR EXECUTIVE OFFICERS
F        BSB STOCKHOLDER AGREEMENT
G        NBT STOCKHOLDER AGREEMENT


                                       iii
<PAGE>   67
                                                                       Exhibit A

                               BANK PLAN OF MERGER

                  This Bank Plan of Merger (this "Plan of Merger") is made and
entered into as of the ____ day of __________, 2000 between NBT BANK, NATIONAL
ASSOCIATION, a national banking association located in Norwich, New York ("NBT
Bank") and BSB Bank & Trust Company, a New York-chartered commercial bank and
trust company located in Binghamton, New York ("BSB Bank").

                                   WITNESSETH

                  WHEREAS, NBT Bancorp Inc., a Delaware corporation ("NBT"), and
BSB Bancorp, Inc., a Delaware corporation ("BSB"), have entered into an
Agreement and Plan of Merger, dated as of April ____, 2000 (the "Agreement");

                  WHEREAS, NBT Bank is a wholly owned subsidiary of NBT and BSB
Bank is a wholly owned subsidiary of BSB;

                  WHEREAS, BSB will merge with and into NBT pursuant to the
terms of the Agreement, and immediately thereafter BSB Bank will merge with and
into NBT Bank pursuant to this Plan of Merger, with NBT Bank surviving as the
resulting bank; and

                  WHEREAS, NBT Bank has _______ shares of common stock
outstanding, $1.00 par value per share, and BSB Bank has 1,000 shares of capital
stock outstanding, $1.00 par value per share.

                  NOW, THEREFORE, in consideration of the premises and the
mutual covenants and agreements contained herein and in the Agreement, the
parties hereto do mutually agree, intending to be legally bound, as follows:

                                    ARTICLE 1
                                   DEFINITIONS

                  Except as otherwise provided herein, the capitalized terms set
forth below shall have the following meanings:

         1.1      "BANK MERGER" shall mean the merger of BSB Bank with and into
NBT Bank as provided in Section 2.1 of this Plan of Merger.

<PAGE>   68

         1.2      "EFFECTIVE TIME" shall mean the date and time at which the
merger contemplated by this Plan of Merger becomes effective as provided in
Section 2.2 hereof.

         1.3      "MERGING BANKS" shall mean, collectively, BSB Bank and NBT
Bank.

         1.4      "OCC" shall mean the Office of the Comptroller of the
Currency.

         1.5      "RESULTING BANK" shall refer to NBT Bank as the surviving bank
in the Bank Merger.

                                    ARTICLE 2
                            TERMS OF THE BANK MERGER

                            2.1      THE BANK MERGER

                  (a)      Subject to the terms and conditions set forth in the
Agreement, and in accordance with the National Bank Act and the Federal Bank
Merger Act and the regulations of the OCC promulgated thereunder, and the New
York Banking Law and the regulations of the New York Banking Board and the New
York Superintendent of Banks, at the Effective Time, BSB Bank shall be merged
with and into NBT Bank pursuant to and upon the terms set forth in this Plan of
Merger. NBT Bank shall continue as the Resulting Bank in the Bank Merger and the
separate existence of BSB Bank shall cease.

                  (b)      As a result of the Bank Merger, (i) each share of
capital stock, par value $1.00 per share, of BSB Bank issued and outstanding
immediately prior to the Effective Time shall be canceled, and (ii) each share
of common stock, par value $1.00 per share, of NBT Bank issued and outstanding
immediately prior to the Effective Time shall remain issued and outstanding and
shall constitute the only shares of common stock of the Surviving Bank issued
and outstanding immediately after the Effective Time.

                  (c)      On and after the Effective Time, the Bank Merger
shall have the effects set forth in Section 215a(c) of the National Bank Act and
Section 602 of the New York Banking Law.

                           2.2      Effective Time

                  The Bank Merger shall become effective (the "Effective Time")
at ______.m. on __________, 2000.


                                      -5-
<PAGE>   69

                           2.3      Name of the Resulting Bank

                  The name of the Resulting Bank shall be "___________________."

                           2.4      Articles of Association

                  On and after the Effective Time, the Articles of Association
of NBT Bank shall be the Articles of Association of the Resulting Bank, unless
and until amended in accordance with applicable law except that the corporate
title shall be changed in accordance with Section 2.3 of this Plan of Merger.

                           2.5      Bylaws

                  On and after the Effective Time, the bylaws of NBT Bank shall
be the bylaws of the Resulting Bank, unless and until amended in accordance with
applicable law except that the corporate title shall be changed in accordance
with Section 2.3 of this Plan of Merger.

                           2.6      Directors and Officers

                  The directors and executive officers of the Resulting Bank
shall be as set forth in Annex 1 hereto.


                           2.7      Corporate Action

                  This Plan of Merger and the consummation of the transactions
contemplated hereby have been duly and validly adopted and approved by at least
a majority of the Board of Directors of NBT Bank and BSB Bank, and the sole
shareholder of each of the Merging Banks.

                           2.8      Offices of the Resulting Bank

                  NBT Bank, as the Resulting Bank, shall relocate its main
office to Binghamton, New York, and shall establish a branch office at its
former main office location and also shall establish as branch offices the
principal office and branch offices of BSB Bank (except the facility, if any, of
BSB that becomes the main office of the Resulting Bank). The location of the
main office and other offices of the Resulting Bank shall be as set forth at
Annex 2 hereto.


                                      -6-
<PAGE>   70

                                    ARTICLE 3
                                  MISCELLANEOUS

                           3.1      Successors

                  This Plan of Merger shall be binding on the successors of NBT
Bank and BSB Bank.

                           3.2      Counterparts

This Plan of Merger may be executed in two counterparts, each of which shall be
 deemed an original, but which taken together shall constitute one and the same
 document.

                            [SIGNATURE PAGE FOLLOWS]


                                      -7-
<PAGE>   71


                  IN WITNESS WHEREOF, each of the parties has caused this Plan
of Merger to be duly executed on its behalf by an officer thereunto duly
authorized, all as of the day and year first above written.

<TABLE>
<S>                                                      <C>
                                                         NBT BANK, NATIONAL ASSOCIATION

ATTEST:

By:                                                      By:
    ----------------------------------                       -----------------------------------
    Name:                                                    Name:  Daryl R. Forsythe
         ----------------------------                        Title: Chairman and Chief Executive
    Title:  Senior Vice President and                               Officer
            Corporate Secretary

                                                         BSB BANK & TRUST COMPANY

ATTEST:

By:                                                      By:
    ----------------------------------                       -----------------------------------
    Name:  Larry G. Denniston                                Name:  Thomas L. Thorn
    Title: Executive Vice President                          Title: Acting President and Chief Executive
           and Secretary                                            Officer
</TABLE>


                                      -8-
<PAGE>   72

                                     ANNEX 1

         DIRECTORS AND OFFICERS OF RESULTING BANK AFTER THE BANK MERGER


<PAGE>   73


                                     ANNEX 2

                 OFFICES OF RESULTING BANK AFTER THE BANK MERGER

                  At the Effective Time of the Bank Merger, NBT Bank will have
the following offices:

Location of Main Office

Location of Branch Offices


                                      -2-
<PAGE>   74

                                                                       EXHIBIT B

                    BSB BANCORP, INC. STOCK OPTION AGREEMENT

                       THE TRANSFER OF THE OPTION GRANTED
              BY THIS AGREEMENT IS SUBJECT TO RESALE RESTRICTIONS.

                  This STOCK OPTION AGREEMENT, dated as of April 19, 2000 (this
"Agreement"), is entered into between BSB Bancorp, Inc., a Delaware corporation
("Issuer"), and NBT Bancorp Inc., a Delaware corporation ("Grantee").

                                   WITNESSETH:

                  WHEREAS, Grantee and Issuer have entered into an Agreement and
Plan of Merger, dated as of even date with this Agreement (the "Plan"), which
was executed by the parties thereto prior to the execution of this Agreement;
and

                  WHEREAS, as a condition and inducement to Grantee's entering
into the Plan and in consideration therefor, Issuer has agreed to grant Grantee
the Option (as defined below).

                  NOW, THEREFORE, in consideration of the foregoing and the
mutual covenants and agreements set forth herein and in the Plan, the parties
hereto agree as follows:

         SECTION 1. Issuer hereby grants to Grantee an irrevocable option (the
"Option") to purchase, subject to the terms hereof, up to a number of fully paid
and nonassessable shares of common stock, par value $0.01 per share of Issuer
("Issuer Common Stock") equal to 19.9% of the total of the number of outstanding
shares of Issuer Common Stock as of the first date that the Option becomes
exercisable, at a price per share equal to $18.50 (the "Option Price") [Note:
The option price will be the closing market price of Issuer common stock as of
the close of business on the day before execution].

         SECTION 2. (a) Grantee may exercise the Option, in whole or part, at
any time and from time to time following the occurrence of a Purchase Event (as
defined below); provided, however, that the Option shall terminate and be of no
further force and effect upon the earliest to occur of the following events
(which are collectively referred to as an "Exercise Termination Event"):

                      (i)  The time immediately prior to the Effective Time;

                      (ii) 12 months after the first occurrence of a Purchase
         Event;


<PAGE>   75

(iii)             12 months after the termination of the Plan following the
  occurrence of a Preliminary Purchase Event (as defined below);

(iv)              upon the termination of the Plan, if no Purchase Event or
  Preliminary Purchase Event has occurred prior to such termination, by Issuer
  pursuant to Section 7.01(d) of the Plan, both parties pursuant to Section
  7.01(a) of the Plan, or by either party pursuant to Section 7.01(b) of the
  Plan;

                      (v)  upon termination of the Plan, by either party
         pursuant to Sections 7.01(e) or (f) of the Plan based on (A) the
         required votes of Grantee's stockholders not being obtained for any
         reason at the NBT Stockholders' Meeting (as defined in the Plan) or (B)
         the required vote of Issuer's stockholders not being received at the
         BSB Stockholders' Meeting (as defined in the Plan), if no Purchase
         Event or Preliminary Purchase Event has occurred prior to the meeting
         of Issuer's stockholders (or any adjournment or postponement thereof)
         held to vote on the Plan; or

(vi)              12 months after the termination of the Plan, by Grantee
  pursuant to Section 7.01(c) thereof as a result of a breach by Issuer, or by
  Grantee or Issuer pursuant to Section 7.01(g) or (h) of the Plan.

                  (b)      The term "Preliminary Purchase Event" shall mean any
of the following events or transactions occurring on or after the date hereof
and prior to an Exercise Termination Event:

                      (i)  Issuer without having received Grantee's prior
         written consent, shall have entered into any letter of intent or
         definitive agreement to engage in an Acquisition Transaction (as
         defined below) with any person (as defined below) other than Grantee or
         any of its subsidiaries (each a "Grantee Subsidiary") or the Board of
         Directors of Issuer shall have recommended that the stockholders of
         Issuer approve or accept any Acquisition Transaction with any Person
         (as the term "person" is defined in Sections 3(a)9 and 13(d)(3) of the
         Exchange Act and the rules and regulations thereunder) other than
         Grantee or any Grantee Subsidiary. For purposes of this Agreement,
         "Acquisition Transaction" shall mean (x) a merger, consolidation or
         other business combination involving Issuer, (y) a purchase, lease or
         other acquisition of all or substantially all of the assets of Issuer,
         (z) a purchase or other acquisition (including by way of merger,
         consolidation, share exchange or otherwise) of Beneficial Ownership (as
         the term "beneficial ownership" is defined in


                                      -2-
<PAGE>   76

         Regulation 13d-3(a) of the Exchange Act) of securities representing 20%
         or more of the voting power of Issuer; provided, however, that
         "Acquisition Transaction" shall not include a transaction entered into
         after the termination of the Plan in which the Issuer is the surviving
         entity, if in connection with such transaction, no person acquires
         Beneficial Ownership of 20% or more of the total voting power of the
         Issuer to be outstanding after giving effect to such transaction and in
         which the aggregate voting power of Issuer acquired by all persons is
         less than 33% of the total voting power of Issuer;

                      (ii) Any Person (other than Grantee, any Grantee
         Subsidiary or any current affiliate of Issuer) shall have acquired
         Beneficial Ownership of 20% or more of the outstanding shares of Issuer
         Common Stock;

                      (iii)(a) Any Person (other than Grantee or any Grantee
         Subsidiary) shall have made a bona fide proposal to Issuer or, by a
         public announcement or written communication that is or becomes the
         subject of public disclosure, to Issuer's stockholders prior to the BSB
         Stockholders' Meeting to engage in an Acquisition Transaction
         (including, without limitation, any situation in which any Person other
         than Grantee or any Grantee Subsidiary shall have commenced (as such
         term is defined in Rule 14d-2 promulgated under the Exchange Act of
         1934, as amended (the "Exchange Act"), or shall have filed a
         registration statement under the Securities Act of 1933, as amended
         (the "Securities Act"), with respect to a tender offer or exchange
         offer to purchase any shares of Issuer Common Stock such that, upon
         consummation of such offer, such person would have Beneficial Ownership
         of 20% or more of the then outstanding shares of Issuer Common Stock
         (such an offer being referred to herein as a "Tender Offer" or an
         "Exchange Offer", respectively) and (b) the stockholders of Issuer do
         not approve the Merger, as defined in the Plan, at the BSB
         Stockholders' Meeting;

                      (iv) There shall exist a willful or intentional breach
         under the Plan by Issuer and such breach would entitle Grantee to
         terminate the Plan; or

                      (v)  The BSB Stockholders' Meeting to be held for the
         purpose of voting on the Plan shall not have been held pursuant to the
         Plan or shall have been canceled prior to termination of the Plan, or
         for any reason whatsoever Issuer's Board of Directors shall have failed
         to recommend, or shall have withdrawn or modified in a manner adverse
         to Grantee the recommendation of Issuer's Board of Directors, that
         Issuer's stockholders approve the Plan, or if Issuer or Issuer's Board
         of Directors


                                      -3-
<PAGE>   77

         fails to oppose any proposal of the type described at Section
         2(b)(iii)(a) above by any Person (other than Grantee or any Grantee
         Subsidiary).

                  (c)      The term "Purchase Event" shall mean any of the
following events or transactions occurring on or after the date hereof and prior
to an Exercise Termination Event:

                      (i)  The acquisition by any Person (other than Grantee or
         any Grantee Subsidiary) of Beneficial Ownership (other than on behalf
         of the Issuer) of 20% or more of the then outstanding Issuer Common
         Stock;

                      (ii) The occurrence of a Preliminary Purchase Event
         described in Section 2(b)(i); or

                      (iii)The termination of the Plan by Grantee pursuant to
         Section 7.01(c) thereof as a result of a willful or intentional breach
         by Issuer or by Grantee or Issuer pursuant to Section 7.01(g) or (h) of
         the Plan.

                  (d)      Issuer shall notify Grantee promptly in writing of
the occurrence of any Preliminary Purchase Event or Purchase Event known to
Issuer; provided, however, that the giving of such notice by Issuer shall not be
a condition to the right of Grantee to exercise the Option.

                  (e)      In the event that Grantee is entitled to and wishes
to exercise the Option, it shall send to Issuer a written notice (the "Option
Notice," the date of which being hereinafter referred to as the "Notice Date")
specifying (i) the total number of shares of Issuer Common Stock it will
purchase pursuant to such exercise and (ii) the time (which shall be on a
business day that is not less than three nor more than 10 business days from the
Notice Date) on which the closing of such purchase shall take place (the
"Closing Date"); such closing to take place at the principal office of the
Issuer; provided, however, that if prior notification to or approval of the
Board of Governors of the Federal Reserve System ("FRB"), Office of the
Comptroller of the Currency ("OCC"), the Federal Trade Commission (the "FTC"),
the Antitrust Division of the Department of Justice ("DOJ") or any other
Governmental Authority is required in connection with such purchase (each, a
"Notification" or an "Approval," as the case may be), at Grantee's sole expense,
(a) Grantee shall promptly file the required notice or application for approval
("Notice/Application"), (b) Grantee shall expeditiously process the
Notice/Application and (c) for the purpose of determining the Closing Date
pursuant to clause (ii) of this sentence, the period of time


                                      -4-
<PAGE>   78

that otherwise would run from the Notice Date shall instead run from the later
of (x) in connection with any Notification, the date on which any required
notification periods have expired or been terminated and (y) in connection with
any Approval, the date on which such approval has been obtained and any
requisite waiting period or periods shall have expired. For purposes of Section
2(a) hereof, any exercise of the Option shall be deemed to occur on the Notice
Date relating thereto. Prior to the Closing Date, Grantee shall have the right
to revoke its exercise of the Option by written notice to the Issuer given not
less than three business days prior to the Closing Date.

                  (f)      At the closing referred to in Section 2(e) hereof,
Grantee shall pay to Issuer the aggregate purchase price for the number of
shares of Issuer Common Stock specified in the Option Notice in immediately
available funds by wire transfer to a bank account designated by Issuer;
provided, however, that failure or refusal of Issuer to designate such a bank
account shall not preclude Grantee from exercising the Option.

                  (g)      At such closing, simultaneously with the delivery of
immediately available funds as provided in Section 2(f) hereof, Issuer shall
deliver to Grantee a certificate or certificates representing the number of
shares of Issuer Common Stock specified in the Option Notice and, if the Option
should be exercised in part only, a new Option evidencing the rights of Grantee
thereof to purchase the balance of the shares of Issuer Common Stock purchasable
hereunder.

                  (h)      Certificates for Issuer Common Stock delivered at a
closing hereunder shall be endorsed with a restrictive legend substantially as
follows:

                           The transfer of the shares represented by this
                  certificate is subject to resale restrictions arising under
                  the Securities Act of 1933, as amended, and applicable state
                  securities laws and to certain provisions of an agreement
                  between BSB Bancorp, Inc. and NBT Bancorp Inc. dated as of
                  April 19, 2000. A copy of such agreement is on file at the
                  principal office of NBT, and will be provided to the holder
                  hereof without charge upon receipt by NBT of a written request
                  therefor.

It is understood and agreed that: (i) the reference to the resale restrictions
of the Securities Act in the above legend shall be removed by delivery of
substitute certificate(s) without such reference if Grantee shall have delivered
to Issuer a copy of a letter from the staff of the Securities and Exchange
Commission (the "SEC") or Governmental Authority responsible for administering
any applicable state securities laws or an opinion of counsel,


                                      -5-
<PAGE>   79

in form and substance satisfactory to Issuer's counsel, to the effect that such
legend is not required for purposes of the Securities Act or applicable state
securities laws; (ii) the reference to the provisions of this Agreement in the
above legend shall be removed by delivery of substitute certificate(s) without
such reference if the shares have been sold or transferred in compliance with
the provisions of this Agreement and under circumstances that do not require the
retention of such reference; and (iii) the legend shall be removed in its
entirety if the conditions in the preceding clauses (i) and (ii) are both
satisfied. In addition such certificates shall bear any other legend as may be
required by law.

                  (i)      Upon the giving by Grantee to Issuer of an Option
Notice and the tender of the applicable purchase price in immediately available
funds on the Closing Date, unless prohibited by applicable law, Grantee shall be
deemed to be the holder of record of the number of shares of Issuer Common Stock
specified in the Option Notice, notwithstanding that the stock transfer books of
Issuer shall then be closed or that certificates representing such shares of
Issuer Common Stock shall not then actually be delivered to Grantee. Issuer
shall pay all expenses and other charges that may be payable in connection with
the preparation, issuance and delivery of stock certificates under this Section
2 in the name of Grantee.

         SECTION 3. Issuer agrees: (i) that it shall at all times until the
termination of this Agreement have reserved for issuance upon the exercise of
the Option that number of authorized and reserved shares of Issuer Common Stock
equal to the maximum number of shares of Issuer Common Stock at any time and
from time to time issuable hereunder, all of which shares will, upon issuance
pursuant hereto, be duly authorized, validly issued, fully paid, non-assessable,
and delivered free and clear of all claims, liens, encumbrances and security
interests and not subject to any preemptive rights; (ii) that it will not, by
amendment of its certificate of incorporation or through reorganization,
consolidation, merger, dissolution or sale of assets, or by any other voluntary
act, avoid or seek to avoid the observance or performance of any of the
covenants, stipulations or conditions to be observed or performed hereunder by
Issuer; (iii) promptly to take all reasonable action as may from time to time be
requested by Grantee, at Grantee's expense (including (x) complying with all
premerger notification, reporting and waiting period requirements specified in
15 U.S.C. Section 18a and regulations promulgated thereunder and (y) in the
event prior approval of or notice to the FRB, OCC, FTC, DOJ or any other
Governmental Authority, under the Hart-Scott-Rodino Antitrust Improvements Act
of 1976, as amended, the Bank Holding Company Act, the Change in Bank Control
Act or any other applicable federal or state law, is necessary before the Option
may be exercised), cooperating with Grantee in preparing such applications or
notices and providing such information to each


                                      -6-
<PAGE>   80

such Governmental Authority as it may require in order to permit Grantee to
exercise the Option and Issuer duly and effectively to issue shares of Issuer
Common Stock pursuant hereto; and (iv) to take all action provided herein to
protect the rights of Grantee against dilution.

         SECTION 4. This Agreement (and the Option granted hereby) are
exchangeable, without expense, at the option of Grantee, upon presentation and
surrender of this Agreement at the principal office of Issuer, for other
agreements providing for Options of different denominations entitling the holder
thereof to purchase, on the same terms and subject to the same conditions as are
set forth herein, in the aggregate the same number of shares of Issuer Common
Stock purchasable hereunder. The terms "Agreement" and "Option" as used herein
include any agreements and related options for which this Agreement (and the
Option granted hereby) may be exchanged. Upon receipt by Issuer of evidence
reasonably satisfactory to it of the loss, theft, destruction or mutilation of
this Agreement, and (in the case of loss, theft or destruction) of reasonably
satisfactory indemnification, and upon surrender and cancellation of this
Agreement, if mutilated, Issuer will execute and deliver a new Agreement of like
tenor and date.

         SECTION 5. The number of shares of Issuer Common Stock purchasable upon
the exercise of the Option shall be subject to adjustment from time to time as
follows:

                  (a)      In the event of any change in the type or number of
shares of Issuer Common Stock by reason of stock dividends, split-ups, mergers,
recapitalizations, combinations, subdivisions, conversions, exchanges of shares
or other issuances of additional shares (other than pursuant to the exercise of
the Option), the type and number of shares of Issuer Common Stock purchasable
upon exercise hereof shall be appropriately adjusted and proper provision shall
be made so that, in the event that any additional shares of Issuer Common Stock
are to be issued or otherwise become outstanding as a result of any such change
(other than pursuant to an exercise of the Option), the number of shares of
Issuer Common Stock that remain subject to the Option shall be increased or
decreased (as applicable) so that, after such issuance and together with the
shares of Issuer Common Stock previously issued pursuant to the prior partial
exercise of the Option (as adjusted on account of any of the foregoing changes
in the Issuer Common Stock), such number of shares shall equal the sum of 19.9%
of the total of the number of shares of Issuer Common Stock issued and
outstanding on the date the Option first becomes exercisable.


                                      -7-
<PAGE>   81

                  (b)      Whenever the number of shares of Issuer Common Stock
purchasable upon exercise hereof is adjusted as provided in this Section 5, the
Option Price shall be adjusted by multiplying the Option Price by a fraction,
the numerator of which shall be equal to the number of shares of Issuer Common
Stock purchasable prior to the adjustment and the denominator of which shall be
equal to the number of shares of Issuer Common Stock purchasable after the
adjustment.

         SECTION 6. (a)  Upon the occurrence of a Purchase Event that occurs
prior to an Exercise Termination Event, Issuer shall, at the request of Grantee
(whether on its own behalf or on behalf of any subsequent holder of the Option
(or part thereof) or of any of the shares of Issuer Common Stock issued pursuant
hereto), promptly prepare, file and keep current a shelf registration statement
with the SEC, under the Securities Act covering any shares issued and issuable
pursuant to the Option and shall use its reasonable best efforts to cause such
registration statement to become effective, and to remain current and effective
for a period not in excess of 90 days from the day such registration statement
first becomes effective, in order to permit the sale or other disposition of any
shares of Issuer Common Stock issued upon total or partial exercise of the
Option ("Option Shares") in accordance with any plan of disposition requested by
Grantee. Grantee shall have the right to demand two such registrations, which
demand right shall be transferable but in no event shall Issuer be required to
effect more than two registrations in the aggregate pursuant to this Option or
any subdivision hereof. Grantee shall provide all information reasonably
requested by Issuer for inclusion in any registration statement to be filed
hereunder. In connection with any such registration statement, Issuer and
Grantee shall provide each other with representations, warranties, indemnities
and other agreements customarily given in connection with such registration. If
requested by Grantee in connection with such registration, Issuer and Grantee
shall become a party to any underwriting agreement relating to the sale of such
shares, but only to the extent of obligating themselves in respect of
representations, warranties, indemnities and other agreements customarily
included in such underwriting agreements and reasonably acceptable to Issuer.
Notwithstanding the foregoing, if Grantee revokes any exercise notice or fails
to exercise any Option with respect to any exercise notice pursuant to Section
2(e) hereof, Issuer shall not be obligated to continue any registration process
with respect to the sale of Option Shares issuable upon the exercise of such
Option and Grantee shall not be deemed to have demanded registration of Option
Shares. If Issuer withdraws a registration statement which has been declared
effective at the request of Grantee, or any subsequent holder, then such filing
shall be deemed an effective registration for all purposes hereunder. The Issuer
will not be required to file any such registration


                                      -8-
<PAGE>   82

statement during any period of time (not to exceed 30 days in the case of
clauses (A) or (C) below or 45 days in the case of clause (B) below) when (A)
the Issuer is in possession of material non-public information which it
reasonably believes would be detrimental to be disclosed at such time and such
information would have to be disclosed if a registration statement were filed at
that time; (B) the Issuer is required under the Securities Act and the rules and
regulations thereunder to include audited financial statements for any period in
such registration statement and such financial statements are not yet available
for inclusion in such registration statement; or (C) the Issuer reasonably
determines that such registration would interfere with any financing,
acquisition or material transaction involving the Issuer. The registration
rights set forth in this Section 6 are subject to the condition that the Grantee
or subsequent holder shall provide the Issuer with such information with respect
to the holder's securities, the plan for distribution thereof, and such other
information with respect to the holder that is required under applicable
securities laws to enable the Issuer to include in a registration statement all
material facts required to be disclosed with respect to a registration
thereunder, including the identity of the holder and the holder's plan of
distribution. The Grantee shall not be able to exercise its registration rights
hereunder if Grantee can rely on Rule 144 promulgated under the Securities Act
to sell such number of shares of Issuer Common Stock that the Grantee otherwise
would seek to register.

                  (b)      Concurrently with the preparation and filing of a
registration statement under Section 6(a) hereof, Issuer shall also make all
filings required to comply with state securities laws in such number of states
as Grantee may reasonably request; provided, that Issuer shall not be required
to qualify to do business in, or consent to service of process in, any
jurisdiction by reason of this provision.

         SECTION 7. Notwithstanding Sections 2 and 6 hereof, if Grantee has
given the notice referred to in one or more of such Sections, the exercise of
the rights specified in any such Section shall be extended (a) if the exercise
of such rights requires obtaining regulatory approvals (including any required
waiting periods) to the extent necessary to obtain all regulatory approvals for
the exercise of such rights, and (b) to the extent necessary to avoid liability
under Section 16(b) of the Exchange Act by reason of such exercise; provided,
that in no event shall any closing date occur more than 12 months after the
related notice date, and, if the closing date shall not have occurred within
such period due to the failure to obtain any required approval by the FRB, OCC,
FTC, DOJ or any other Governmental Authority despite the reasonable best efforts
of Grantee and Issuer to obtain such approvals, the exercise of the rights shall
be deemed to have been rescinded as of the related notice date. In the event (a)
Grantee receives official notice that an approval


                                      -9-
<PAGE>   83

of the FRB, OCC, FTC, DOJ or any other Governmental Authority required for the
purchase and sale of the Option Shares will not be issued or granted or (b) a
closing date has not occurred within 12 months after the related notice date due
to the failure to obtain any such required approval, Grantee shall be entitled
to exercise the Option in connection with the concurrent resale of the Option
Shares pursuant to a registration statement as provided in Section 6 hereof.

         SECTION 8. Issuer hereby represents and warrants to Grantee as follows:

                  (a)      Issuer has the requisite corporate power and
authority to execute and deliver this Agreement and to consummate the
transactions contemplated hereby. The execution and delivery of this Agreement
and the consummation of the transactions contemplated hereby have been duly
approved by the Board of Directors of Issuer and no other corporate proceedings
on the part of Issuer are necessary to authorize this Agreement or to consummate
the transactions so contemplated. This Agreement has been duly executed and
delivered by, and constitutes a valid and binding obligation of, Issuer,
enforceable against Issuer in accordance with its terms, subject to any required
Governmental Approval, and except as enforceability thereof may be limited by
applicable bankruptcy, insolvency, reorganization, moratorium and other similar
laws affecting the enforcement of creditors' rights generally and general
principles of equity.

                  (b)      Issuer has taken all necessary corporate action to
authorize and reserve and to permit it to issue, and at all times from the date
hereof through the termination of this Agreement in accordance with its terms
will have reserved for issuance upon the exercise of the Option, that number of
shares of Issuer Common Stock equal to the maximum number of shares of Issuer
Common Stock at any time and from time to time issuable hereunder, and all such
shares, upon issuance pursuant hereto, will be duly authorized, validly issued,
fully paid, non-assessable, and will be delivered free and clear of all claims,
liens, encumbrances and security interests and not subject to any preemptive
rights.

         SECTION 9. (a) Neither of the parties hereto may assign any of its
rights or delegate any of its obligations under this Agreement or the Option
created hereunder to any other Person without the express written consent of the
other party, except that Grantee may assign this Agreement to a wholly owned
subsidiary of Grantee and Grantee may assign its rights hereunder in whole or in
part after the occurrence of a Preliminary Purchase Event. The term "Grantee" as
used in this Agreement shall also be deemed to refer to Grantee's permitted
assigns.


                                      -10-
<PAGE>   84

                  (b)      Any assignment of rights of Grantee to any permitted
assignee of Grantee hereunder shall bear the restrictive legend at the beginning
thereof substantially as follows:

                  The transfer of the option represented by this assignment and
         the related option agreement is subject to resale restrictions arising
         under the Securities Act of 1933, as amended, and applicable state
         securities laws and to certain provisions of an agreement between BSB
         Bancorp, Inc. and NBT Bancorp Inc., dated as of April 19, 2000. A copy
         of such agreement is on file at the principal office of NBT, and will
         be provided to any permitted assignee of the Option without charge upon
         receipt of a written request therefor.

         SECTION 10. Each of Grantee and Issuer will use its reasonable efforts
to make all filings with, and to obtain consents of, all third parties
including, if applicable, the FRB, OCC, FTC, DOJ and other Governmental
Authorities necessary to the consummation of the transactions contemplated by
this Agreement.

         SECTION 11. The parties hereto acknowledge that damages would be an
inadequate remedy for a breach of this Agreement by either party hereto and that
the obligations of the parties hereto shall be enforceable by either party
hereto through injunctive or other equitable relief. Both parties further agree
to waive any requirement for the securing or posting of any bond in connection
with the obtaining of any such equitable relief and that this provision is
without prejudice to any other rights that the parties hereto may have for any
failure to perform this Agreement.

         SECTION 12. If any term, provision, covenant or restriction contained
in this Agreement is held by a court or a federal or state regulatory agency of
competent jurisdiction to be invalid, void or unenforceable, the remainder of
the terms, provisions and covenants and restrictions contained in this Agreement
shall remain in full force and effect, and shall in no way be affected, impaired
or invalidated. If for any reason such court or regulatory agency determines
that Grantee is not permitted to acquire the full number of shares of Issuer
Common Stock provided in Section 1 hereof (as adjusted pursuant hereto), it is
the express intention of Issuer to allow Grantee to acquire or to require Issuer
to repurchase such lesser number of shares as may be permissible without any
amendment or modification hereof.


                                      -11-
<PAGE>   85

         SECTION 13. All notices, requests, claims, demands and other
communications hereunder shall be deemed to have been duly given when delivered
in the manner and at the respective addresses of the parties set forth in the
Plan.

         SECTION 14. This Agreement, the rights and obligations of the parties
hereto, and any claims or disputes relating thereto shall be governed by and
construed in accordance with the laws of the State of Delaware (but not
including the choice of law rules thereof).

         SECTION 15. This Agreement may be executed in counterparts, each of
which shall be deemed to be an original, but all of which shall constitute one
and the same agreement and shall be effective at the time of execution and
delivery.

         SECTION 16. Except as otherwise expressly provided herein, each of the
parties hereto shall bear and pay all costs and expenses incurred by it or on
its behalf in connection with the transactions contemplated hereunder.

         SECTION 17. Except as otherwise expressly provided herein or in the
Plan, this Agreement contains the entire agreement between the parties with
respect to the transactions contemplated hereunder and supersedes all prior
arrangements or understandings with respect thereof, written or oral. The terms
and conditions of this Agreement shall inure to the benefit of and be binding
upon the parties hereto and their respective successors and permitted assigns.
Nothing in this Agreement, expressed or implied, is intended to confer upon any
party, other than the parties hereto, and their respective successors except as
assigns, any rights, remedies, obligations or liabilities under or by reason of
this Agreement, except as expressly provided herein.

         SECTION 18. Capitalized terms used in this Agreement and not defined
herein but defined in the Plan shall have the meanings assigned therein.

         SECTION 19. Nothing contained in this Agreement shall be deemed to
authorize or require Issuer or Grantee to breach any provision of the Plan or
any provision of law applicable to the Grantee or Issuer.

         SECTION 20. In the event that any selection or determination is to be
made by Grantee or a subsequent holder hereunder and at the time of such
selection or determination there is more than one Grantee or holders, such
selection shall be made by a majority in interest of such Grantees or holders.


                                      -12-
<PAGE>   86

         SECTION 21. In the event of any exercise of the option by Grantee,
Issuer and such Grantee shall execute and deliver all other documents and
instruments and take all other action that may be reasonably necessary in order
to consummate the transactions provided for by such exercise.

         SECTION 22. Except to the extent Grantee exercises the Option, Grantee
shall have no rights to vote or receive dividends or have any other rights as a
shareholder with respect to shares of Issuer Common Stock covered hereby.

                            [SIGNATURE PAGE FOLLOWS]


                                      -13-
<PAGE>   87

         IN WITNESS WHEREOF, each of the parties has caused this Option
Agreement to be executed and delivered on its behalf by their respective
officers thereunto duly authorized, all as of the date first above written.

                                    BSB BANCORP, INC.

                                    By:    /s/ Thomas L. Thorn
                                       ---------------------------------
                                    Name:  Thomas L. Thorn

                                    Title: Acting President and Chief Executive

                                           Officer


                                    NBT BANCORP INC.

                                    By:    /s/ Daryl R. Forsythe
                                       ---------------------------------
                                    Name:  Daryl R. Forsythe

                                    Title: President and Chief Executive

                                           Officer


<PAGE>   88

                                                                       EXHIBIT C

                     NBT BANCORP INC. STOCK OPTION AGREEMENT

                       THE TRANSFER OF THE OPTION GRANTED
              BY THIS AGREEMENT IS SUBJECT TO RESALE RESTRICTIONS.

                  This STOCK OPTION AGREEMENT, dated as of April 19, 2000 (this
"Agreement"), is entered into between NBT Bancorp Inc., a Delaware corporation
("Issuer"), and BSB Bancorp, Inc., a Delaware corporation ("Grantee").

                                   WITNESSETH:

                  WHEREAS, Grantee and Issuer have entered into an Agreement and
Plan of Merger, dated as of even date with this Agreement (the "Plan"), which
was executed by the parties thereto prior to the execution of this Agreement;
and

                  WHEREAS, as a condition and inducement to Grantee's entering
into the Plan and in consideration therefor, Issuer has agreed to grant Grantee
the Option (as defined below).

                  NOW, THEREFORE, in consideration of the foregoing and the
mutual covenants and agreements set forth herein and in the Plan, the parties
hereto agree as follows:

         SECTION 1. Issuer hereby grants to Grantee an irrevocable option (the
"Option") to purchase, subject to the terms hereof, up to a number of fully paid
and nonassessable shares of common stock, par value $0.01 per share of Issuer
("Issuer Common Stock") equal to 19.9% of the total of the number of outstanding
shares of Issuer Common Stock as of the first date that the Option becomes
exercisable, at a price per share equal to $12.13 (the "Option Price") [Note:
The option price will be the closing market price of Issuer common stock as of
the close of business on the day before execution].

         SECTION 2. (a) Grantee may exercise the Option, in whole or part, at
any time and from time to time following the occurrence of a Purchase Event (as
defined below); provided, however, that the Option shall terminate and be of no
further force and effect upon the earliest to occur of the following events
(which are collectively referred to as an "Exercise Termination Event"):

                      (i)  The time immediately prior to the Effective Time;

                      (ii) 12 months after the first occurrence of a Purchase
         Event;

<PAGE>   89

                      (iii) 12 months after the termination of the Plan
         following the occurrence of a Preliminary Purchase Event (as defined
         below);

                      (iv) upon the termination of the Plan, if no Purchase
         Event or Preliminary Purchase Event has occurred prior to such
         termination, by Issuer pursuant to Section 7.01(c) of the Plan, both
         parties pursuant to Section 7.01(a) of the Plan, or by either party
         pursuant to Section 7.01(b) of the Plan;

                      (v)  upon termination of the Plan, by either party
         pursuant to Sections 7.01(e) or (f) of the Plan based on (A) the
         required vote of Grantee's stockholders not being obtained for any
         reason at the BSB Stockholders' Meeting (as defined in the Plan) or (B)
         the required vote of Issuer's stockholders not being received at the
         NBT Stockholders' Meeting (as defined in the Plan), if no Purchase
         Event or Preliminary Purchase Event has occurred prior to the meeting
         of Issuer's stockholders (or any adjournment or postponement thereof)
         held to vote on the Plan; or

                      (vi)  12 months after the termination of the Plan, by
         Grantee pursuant to Section 7.01(d) thereof as a result of a breach
         by Issuer, or by Grantee or Issuer pursuant to Section 7.01(g) or (h)
         of the Plan.

                  (b)      The term "Preliminary Purchase Event" shall mean any
of the following events or transactions occurring on or after the date hereof
and prior to an Exercise Termination Event:

                      (i)  Issuer without having received Grantee's prior
         written consent, shall have entered into any letter of intent or
         definitive agreement to engage in an Acquisition Transaction (as
         defined below) with any person (as defined below) other than Grantee or
         any of its subsidiaries (each a "Grantee Subsidiary") or the Board of
         Directors of Issuer shall have recommended that the stockholders of
         Issuer approve or accept any Acquisition Transaction with any Person
         (as the term "person" is defined in Sections 3(a)9 and 13(d)(3) of the
         Exchange Act and the rules and regulations thereunder) other than
         Grantee or any Grantee Subsidiary. For purposes of this Agreement,
         "Acquisition Transaction" shall mean (x) a merger, consolidation or
         other business combination involving Issuer, (y) a purchase, lease or
         other acquisition of all or substantially all of the assets of Issuer,
         (z) a purchase or other acquisition (including by way of merger,
         consolidation, share exchange or otherwise) of Beneficial Ownership (as
         the term "beneficial ownership" is defined in Regulation 13d-3(a) of
         the Exchange Act) of securities representing 20% or more of


                                      -2-
<PAGE>   90

         the voting power of Issuer; provided, however, that "Acquisition
         Transaction" shall not include a transaction entered into after the
         termination of the Plan in which the Issuer is the surviving entity, if
         in connection with such transaction, no person acquires Beneficial
         Ownership of 20% or more of the total voting power of the Issuer to be
         outstanding after giving effect to such transaction and in which the
         aggregate voting power of Issuer acquired by all persons is less than
         33% of the total voting power of Issuer;

                      (ii) Any Person (other than Grantee, any Grantee
         Subsidiary or any current affiliate of Issuer) shall have acquired
         Beneficial Ownership of 20% or more of the outstanding shares of Issuer
         Common Stock;

                      (iii)(a) Any Person (other than Grantee or any Grantee
         Subsidiary) shall have made a bona fide proposal to Issuer or, by a
         public announcement or written communication that is or becomes the
         subject of public disclosure, to Issuer's stockholders prior to the NBT
         Stockholders' Meeting to engage in an Acquisition Transaction
         (including, without limitation, any situation in which any Person other
         than Grantee or any Grantee Subsidiary shall have commenced (as such
         term is defined in Rule 14d-2 promulgated under the Exchange Act of
         1934, as amended (the "Exchange Act"), or shall have filed a
         registration statement under the Securities Act of 1933, as amended
         (the "Securities Act"), with respect to a tender offer or exchange
         offer to purchase any shares of Issuer Common Stock such that, upon
         consummation of such offer, such person would have Beneficial Ownership
         of 20% or more of the then outstanding shares of Issuer Common Stock
         (such an offer being referred to herein as a "Tender Offer" or an
         "Exchange Offer", respectively) and (b) the stockholders of Issuer do
         not approve the Merger, as defined in the Plan, at the NBT
         Stockholders' Meeting;

                      (iv) There shall exist a willful or intentional breach
         under the Plan by Issuer and such breach would entitle Grantee to
         terminate the Plan; or

                      (v)  The NBT Stockholders' Meeting to be held for the
         purpose of voting on the Plan shall not have been held pursuant to the
         Plan or shall have been canceled prior to termination of the Plan, or
         for any reason whatsoever Issuer's Board of Directors shall have failed
         to recommend, or shall have withdrawn or modified in a manner adverse
         to Grantee the recommendation of Issuer's Board of Directors, that
         Issuer's stockholders approve the Plan, or if Issuer or Issuer's Board
         of Directors



                                      -3-
<PAGE>   91

         fails to oppose any proposal of the type described at Section
         2(b)(iii)(a) above by any Person (other than Grantee or any Grantee
         Subsidiary).

                  (c)      The term "Purchase Event" shall mean any of the
following events or transactions occurring on or after the date hereof and prior
to an Exercise Termination Event:

                      (i)  The acquisition by any Person (other than Grantee or
         any Grantee Subsidiary) of Beneficial Ownership (other than on behalf
         of the Issuer) of 20% or more of the then outstanding Issuer Common
         Stock;

                      (ii) The occurrence of a Preliminary Purchase Event
described in Section 2(b)(i); or

                      (iii)The termination of the Plan by Grantee pursuant to
         Section 7.01(d) thereof as a result of a willful or intentional breach
         by Issuer or by Grantee or Issuer pursuant to Section 7.01(g) or (h) of
         the Plan.

                  (d)      Issuer shall notify Grantee promptly in writing of
the occurrence of any Preliminary Purchase Event or Purchase Event known to
Issuer; provided, however, that the giving of such notice by Issuer shall not be
a condition to the right of Grantee to exercise the Option.

                  (e)      In the event that Grantee is entitled to and wishes
to exercise the Option, it shall send to Issuer a written notice (the "Option
Notice," the date of which being hereinafter referred to as the "Notice Date")
specifying (i) the total number of shares of Issuer Common Stock it will
purchase pursuant to such exercise and (ii) the time (which shall be on a
business day that is not less than three nor more than 10 business days from the
Notice Date) on which the closing of such purchase shall take place (the
"Closing Date"); such closing to take place at the principal office of the
Issuer; provided, however, that if prior notification to or approval of the
Board of Governors of the Federal Reserve System ("FRB"), Office of the
Comptroller of the Currency ("OCC"), the Federal Trade Commission (the "FTC"),
the Antitrust Division of the Department of Justice ("DOJ") or any other
Governmental Authority is required in connection with such purchase (each, a
"Notification" or an "Approval," as the case may be), at Grantee's sole expense,
(a) Grantee shall promptly file the required notice or application for approval
("Notice/Application"), (b) Grantee shall expeditiously process the
Notice/Application and (c) for the purpose of determining the Closing Date
pursuant to clause (ii) of this sentence, the period of time


                                      -4-
<PAGE>   92

that otherwise would run from the Notice Date shall instead run from the later
of (x) in connection with any Notification, the date on which any required
notification periods have expired or been terminated and (y) in connection with
any Approval, the date on which such approval has been obtained and any
requisite waiting period or periods shall have expired. For purposes of Section
2(a) hereof, any exercise of the Option shall be deemed to occur on the Notice
Date relating thereto. Prior to the Closing Date, Grantee shall have the right
to revoke its exercise of the Option by written notice to the Issuer given not
less than three business days prior to the Closing Date.

                  (f)      At the closing referred to in Section 2(e) hereof,
Grantee shall pay to Issuer the aggregate purchase price for the number of
shares of Issuer Common Stock specified in the Option Notice in immediately
available funds by wire transfer to a bank account designated by Issuer;
provided, however, that failure or refusal of Issuer to designate such a bank
account shall not preclude Grantee from exercising the Option.

                  (g)      At such closing, simultaneously with the delivery of
immediately available funds as provided in Section 2(f) hereof, Issuer shall
deliver to Grantee a certificate or certificates representing the number of
shares of Issuer Common Stock specified in the Option Notice and, if the Option
should be exercised in part only, a new Option evidencing the rights of Grantee
thereof to purchase the balance of the shares of Issuer Common Stock purchasable
hereunder.

                  (h)      Certificates for Issuer Common Stock delivered at a
closing hereunder shall be endorsed with a restrictive legend substantially as
follows:

                           The transfer of the shares represented by this
                  certificate is subject to resale restrictions arising under
                  the Securities Act of 1933, as amended, and applicable state
                  securities laws and to certain provisions of an agreement
                  between NBT Bancorp Inc. and BSB Bancorp, Inc. dated as of
                  April 19, 2000. A copy of such agreement is on file at the
                  principal office of BSB, and will be provided to the holder
                  hereof without charge upon receipt by BSB of a written request
                  therefor.

It is understood and agreed that: (i) the reference to the resale restrictions
of the Securities Act in the above legend shall be removed by delivery of
substitute certificate(s) without such reference if Grantee shall have delivered
to Issuer a copy of a letter from the staff of the Securities and Exchange
Commission (the "SEC") or Governmental Authority responsible for administering
any applicable state securities laws or an opinion of counsel,


                                      -5-
<PAGE>   93

in form and substance satisfactory to Issuer's counsel, to the effect that such
legend is not required for purposes of the Securities Act or applicable state
securities laws; (ii) the reference to the provisions of this Agreement in the
above legend shall be removed by delivery of substitute certificate(s) without
such reference if the shares have been sold or transferred in compliance with
the provisions of this Agreement and under circumstances that do not require the
retention of such reference; and (iii) the legend shall be removed in its
entirety if the conditions in the preceding clauses (i) and (ii) are both
satisfied. In addition such certificates shall bear any other legend as may be
required by law.

                  (i)      Upon the giving by Grantee to Issuer of an Option
Notice and the tender of the applicable purchase price in immediately available
funds on the Closing Date, unless prohibited by applicable law, Grantee shall be
deemed to be the holder of record of the number of shares of Issuer Common Stock
specified in the Option Notice, notwithstanding that the stock transfer books of
Issuer shall then be closed or that certificates representing such shares of
Issuer Common Stock shall not then actually be delivered to Grantee. Issuer
shall pay all expenses and other charges that may be payable in connection with
the preparation, issuance and delivery of stock certificates under this Section
2 in the name of Grantee.

         SECTION 3. Issuer agrees: (i) that it shall at all times until the
termination of this Agreement have reserved for issuance upon the exercise of
the Option that number of authorized and reserved shares of Issuer Common Stock
equal to the maximum number of shares of Issuer Common Stock at any time and
from time to time issuable hereunder, all of which shares will, upon issuance
pursuant hereto, be duly authorized, validly issued, fully paid, non-assessable,
and delivered free and clear of all claims, liens, encumbrances and security
interests and not subject to any preemptive rights; (ii) that it will not, by
amendment of its certificate of incorporation or through reorganization,
consolidation, merger, dissolution or sale of assets, or by any other voluntary
act, avoid or seek to avoid the observance or performance of any of the
covenants, stipulations or conditions to be observed or performed hereunder by
Issuer; (iii) promptly to take all reasonable action as may from time to time be
requested by Grantee, at Grantee's expense (including (x) complying with all
premerger notification, reporting and waiting period requirements specified in
15 U.S.C. Section 18a and regulations promulgated thereunder and (y) in the
event prior approval of or notice to the FRB, OCC, FTC, DOJ or any other
Governmental Authority, under the Hart-Scott-Rodino Antitrust Improvements Act
of 1976, as amended, the Bank Holding Company Act, the Change in Bank Control
Act or any other applicable federal or state law, is necessary before the Option
may be exercised), cooperating with Grantee in preparing such applications or
notices and providing such information to each


                                      -6-
<PAGE>   94

such Governmental Authority as it may require in order to permit Grantee to
exercise the Option and Issuer duly and effectively to issue shares of Issuer
Common Stock pursuant hereto; and (iv) to take all action provided herein to
protect the rights of Grantee against dilution.

         SECTION 4. This Agreement (and the Option granted hereby) are
exchangeable, without expense, at the option of Grantee, upon presentation and
surrender of this Agreement at the principal office of Issuer, for other
agreements providing for Options of different denominations entitling the holder
thereof to purchase, on the same terms and subject to the same conditions as are
set forth herein, in the aggregate the same number of shares of Issuer Common
Stock purchasable hereunder. The terms "Agreement" and "Option" as used herein
include any agreements and related options for which this Agreement (and the
Option granted hereby) may be exchanged. Upon receipt by Issuer of evidence
reasonably satisfactory to it of the loss, theft, destruction or mutilation of
this Agreement, and (in the case of loss, theft or destruction) of reasonably
satisfactory indemnification, and upon surrender and cancellation of this
Agreement, if mutilated, Issuer will execute and deliver a new Agreement of like
tenor and date.

         SECTION 5. The number of shares of Issuer Common Stock purchasable upon
the exercise of the Option shall be subject to adjustment from time to time as
follows:

                  (a)      In the event of any change in the type or number of
shares of Issuer Common Stock by reason of stock dividends, split-ups, mergers,
recapitalizations, combinations, subdivisions, conversions, exchanges of shares
or other issuances of additional shares (other than pursuant to the exercise of
the Option), the type and number of shares of Issuer Common Stock purchasable
upon exercise hereof shall be appropriately adjusted and proper provision shall
be made so that, in the event that any additional shares of Issuer Common Stock
are to be issued or otherwise become outstanding as a result of any such change
(other than pursuant to an exercise of the Option), the number of shares of
Issuer Common Stock that remain subject to the Option shall be increased or
decreased (as applicable) so that, after such issuance and together with the
shares of Issuer Common Stock previously issued pursuant to the prior partial
exercise of the Option (as adjusted on account of any of the foregoing changes
in the Issuer Common Stock), such number of shares shall equal the sum of 19.9%
of the total of the number of shares of Issuer Common Stock issued and
outstanding on the date the Option first becomes exercisable.


                                      -7-
<PAGE>   95

                  (b)      Whenever the number of shares of Issuer Common Stock
purchasable upon exercise hereof is adjusted as provided in this Section 5, the
Option Price shall be adjusted by multiplying the Option Price by a fraction,
the numerator of which shall be equal to the number of shares of Issuer Common
Stock purchasable prior to the adjustment and the denominator of which shall be
equal to the number of shares of Issuer Common Stock purchasable after the
adjustment.

         SECTION 6. (a)  Upon the occurrence of a Purchase Event that occurs
prior to an Exercise Termination Event, Issuer shall, at the request of Grantee
(whether on its own behalf or on behalf of any subsequent holder of the Option
(or part thereof) or of any of the shares of Issuer Common Stock issued pursuant
hereto), promptly prepare, file and keep current a shelf registration statement
with the SEC, under the Securities Act covering any shares issued and issuable
pursuant to the Option and shall use its reasonable best efforts to cause such
registration statement to become effective, and to remain current and effective
for a period not in excess of 90 days from the day such registration statement
first becomes effective, in order to permit the sale or other disposition of any
shares of Issuer Common Stock issued upon total or partial exercise of the
Option ("Option Shares") in accordance with any plan of disposition requested by
Grantee. Grantee shall have the right to demand two such registrations, which
demand right shall be transferable but in no event shall Issuer be required to
effect more than two registrations in the aggregate pursuant to this Option or
any subdivision hereof. Grantee shall provide all information reasonably
requested by Issuer for inclusion in any registration statement to be filed
hereunder. In connection with any such registration statement, Issuer and
Grantee shall provide each other with representations, warranties, indemnities
and other agreements customarily given in connection with such registration. If
requested by Grantee in connection with such registration, Issuer and Grantee
shall become a party to any underwriting agreement relating to the sale of such
shares, but only to the extent of obligating themselves in respect of
representations, warranties, indemnities and other agreements customarily
included in such underwriting agreements and reasonably acceptable to Issuer.
Notwithstanding the foregoing, if Grantee revokes any exercise notice or fails
to exercise any Option with respect to any exercise notice pursuant to Section
2(e) hereof, Issuer shall not be obligated to continue any registration process
with respect to the sale of Option Shares issuable upon the exercise of such
Option and Grantee shall not be deemed to have demanded registration of Option
Shares. If Issuer withdraws a registration statement which has been declared
effective at the request of Grantee, or any subsequent holder, then such filing
shall be deemed an effective registration for all purposes hereunder. The Issuer
will not be required to file any such registration


                                      -8-
<PAGE>   96

statement during any period of time (not to exceed 30 days in the case of
clauses (A) or (C) below or 45 days in the case of clause (B) below) when (A)
the Issuer is in possession of material non-public information which it
reasonably believes would be detrimental to be disclosed at such time and such
information would have to be disclosed if a registration statement were filed at
that time; (B) the Issuer is required under the Securities Act and the rules and
regulations thereunder to include audited financial statements for any period in
such registration statement and such financial statements are not yet available
for inclusion in such registration statement; or (C) the Issuer reasonably
determines that such registration would interfere with any financing,
acquisition or material transaction involving the Issuer. The registration
rights set forth in this Section 6 are subject to the condition that the Grantee
or subsequent holder shall provide the Issuer with such information with respect
to the holder's securities, the plan for distribution thereof, and such other
information with respect to the holder that is required under applicable
securities laws to enable the Issuer to include in a registration statement all
material facts required to be disclosed with respect to a registration
thereunder, including the identity of the holder and the holder's plan of
distribution. The Grantee shall not be able to exercise its registration rights
hereunder if Grantee can rely on Rule 144 promulgated under the Securities Act
to sell such number of shares of Issuer Common Stock that the Grantee otherwise
would seek to register.

                  (b)      Concurrently with the preparation and filing of a
registration statement under Section 6(a) hereof, Issuer shall also make all
filings required to comply with state securities laws in such number of states
as Grantee may reasonably request; provided, that Issuer shall not be required
to qualify to do business in, or consent to service of process in, any
jurisdiction by reason of this provision.

         SECTION 7. Notwithstanding Sections 2 and 6 hereof, if Grantee has
given the notice referred to in one or more of such Sections, the exercise of
the rights specified in any such Section shall be extended (a) if the exercise
of such rights requires obtaining regulatory approvals (including any required
waiting periods) to the extent necessary to obtain all regulatory approvals for
the exercise of such rights, and (b) to the extent necessary to avoid liability
under Section 16(b) of the Exchange Act by reason of such exercise; provided,
that in no event shall any closing date occur more than 12 months after the
related notice date, and, if the closing date shall not have occurred within
such period due to the failure to obtain any required approval by the FRB, OCC,
FTC, DOJ or any other Governmental Authority despite the reasonable best efforts
of Grantee and Issuer to obtain such approvals, the exercise of the rights shall
be deemed to have been rescinded as of the related notice date. In the event (a)
Grantee receives official notice that an approval


                                      -9-
<PAGE>   97

of the FRB, OCC, FTC, DOJ or any other Governmental Authority required for the
purchase and sale of the Option Shares will not be issued or granted or (b) a
closing date has not occurred within 12 months after the related notice date due
to the failure to obtain any such required approval, Grantee shall be entitled
to exercise the Option in connection with the concurrent resale of the Option
Shares pursuant to a registration statement as provided in Section 6 hereof.

         SECTION 8. Issuer hereby represents and warrants to Grantee as follows:

                  (a)      Issuer has the requisite corporate power and
authority to execute and deliver this Agreement and to consummate the
transactions contemplated hereby. The execution and delivery of this Agreement
and the consummation of the transactions contemplated hereby have been duly
approved by the Board of Directors of Issuer and no other corporate proceedings
on the part of Issuer are necessary to authorize this Agreement or to consummate
the transactions so contemplated. This Agreement has been duly executed and
delivered by, and constitutes a valid and binding obligation of, Issuer,
enforceable against Issuer in accordance with its terms, subject to any required
Governmental Approval, and except as enforceability thereof may be limited by
applicable bankruptcy, insolvency, reorganization, moratorium and other similar
laws affecting the enforcement of creditors' rights generally and general
principles of equity.

                  (b)      Issuer has taken all necessary corporate action to
authorize and reserve and to permit it to issue, and at all times from the date
hereof through the termination of this Agreement in accordance with its terms
will have reserved for issuance upon the exercise of the Option, that number of
shares of Issuer Common Stock equal to the maximum number of shares of Issuer
Common Stock at any time and from time to time issuable hereunder, and all such
shares, upon issuance pursuant hereto, will be duly authorized, validly issued,
fully paid, non-assessable, and will be delivered free and clear of all claims,
liens, encumbrances and security interests and not subject to any preemptive
rights.

         SECTION 9. (a) Neither of the parties hereto may assign any of its
rights or delegate any of its obligations under this Agreement or the Option
created hereunder to any other Person without the express written consent of the
other party, except that Grantee may assign this Agreement to a wholly owned
subsidiary of Grantee and Grantee may assign its rights hereunder in whole or in
part after the occurrence of a Preliminary Purchase Event. The term "Grantee" as
used in this Agreement shall also be deemed to refer to Grantee's permitted
assigns.


                                      -10-
<PAGE>   98

                  (b)      Any assignment of rights of Grantee to any permitted
assignee of Grantee hereunder shall bear the restrictive legend at the beginning
thereof substantially as follows:

                  The transfer of the option represented by this assignment and
         the related option agreement is subject to resale restrictions arising
         under the Securities Act of 1933, as amended, and applicable state
         securities laws and to certain provisions of an agreement between NBT
         Bancorp Inc. and BSB Bancorp, Inc., dated as of April 19, 2000. A copy
         of such agreement is on file at the principal office of BSB, and will
         be provided to any permitted assignee of the Option without charge upon
         receipt of a written request therefor.

         SECTION 10. Each of Grantee and Issuer will use its reasonable efforts
to make all filings with, and to obtain consents of, all third parties
including, if applicable, the FRB, OCC, FTC, DOJ and other Governmental
Authorities necessary to the consummation of the transactions contemplated by
this Agreement.

         SECTION 11. The parties hereto acknowledge that damages would be an
inadequate remedy for a breach of this Agreement by either party hereto and that
the obligations of the parties hereto shall be enforceable by either party
hereto through injunctive or other equitable relief. Both parties further agree
to waive any requirement for the securing or posting of any bond in connection
with the obtaining of any such equitable relief and that this provision is
without prejudice to any other rights that the parties hereto may have for any
failure to perform this Agreement.

         SECTION 12. If any term, provision, covenant or restriction contained
in this Agreement is held by a court or a federal or state regulatory agency of
competent jurisdiction to be invalid, void or unenforceable, the remainder of
the terms, provisions and covenants and restrictions contained in this Agreement
shall remain in full force and effect, and shall in no way be affected, impaired
or invalidated. If for any reason such court or regulatory agency determines
that Grantee is not permitted to acquire the full number of shares of Issuer
Common Stock provided in Section 1 hereof (as adjusted pursuant hereto), it is
the express intention of Issuer to allow Grantee to acquire or to require Issuer
to repurchase such lesser number of shares as may be permissible without any
amendment or modification hereof.


                                      -11-
<PAGE>   99

         SECTION 13. All notices, requests, claims, demands and other
communications hereunder shall be deemed to have been duly given when delivered
in the manner and at the respective addresses of the parties set forth in the
Plan.

         SECTION 14. This Agreement, the rights and obligations of the parties
hereto, and any claims or disputes relating thereto shall be governed by and
construed in accordance with the laws of the State of Delaware (but not
including the choice of law rules thereof).

         SECTION 15. This Agreement may be executed in counterparts, each of
which shall be deemed to be an original, but all of which shall constitute one
and the same agreement and shall be effective at the time of execution and
delivery.

         SECTION 16. Except as otherwise expressly provided herein, each of the
parties hereto shall bear and pay all costs and expenses incurred by it or on
its behalf in connection with the transactions contemplated hereunder.

         SECTION 17. Except as otherwise expressly provided herein or in the
Plan, this Agreement contains the entire agreement between the parties with
respect to the transactions contemplated hereunder and supersedes all prior
arrangements or understandings with respect thereof, written or oral. The terms
and conditions of this Agreement shall inure to the benefit of and be binding
upon the parties hereto and their respective successors and permitted assigns.
Nothing in this Agreement, expressed or implied, is intended to confer upon any
party, other than the parties hereto, and their respective successors except as
assigns, any rights, remedies, obligations or liabilities under or by reason of
this Agreement, except as expressly provided herein.

         SECTION 18. Capitalized terms used in this Agreement and not defined
herein but defined in the Plan shall have the meanings assigned therein.

         SECTION 19. Nothing contained in this Agreement shall be deemed to
authorize or require Issuer or Grantee to breach any provision of the Plan or
any provision of law applicable to the Grantee or Issuer.

         SECTION 20. In the event that any selection or determination is to be
made by Grantee or a subsequent holder hereunder and at the time of such
selection or determination there is more than one Grantee or holders, such
selection shall be made by a majority in interest of such Grantees or holders.


                                      -12-
<PAGE>   100

         SECTION 21. In the event of any exercise of the option by Grantee,
Issuer and such Grantee shall execute and deliver all other documents and
instruments and take all other action that may be reasonably necessary in order
to consummate the transactions provided for by such exercise.

         SECTION 22. Except to the extent Grantee exercises the Option, Grantee
shall have no rights to vote or receive dividends or have any other rights as a
shareholder with respect to shares of Issuer Common Stock covered hereby.

                            [SIGNATURE PAGE FOLLOWS]


                                      -13-
<PAGE>   101


         IN WITNESS WHEREOF, each of the parties has caused this Option
Agreement to be executed and delivered on its behalf by their respective
officers thereunto duly authorized, all as of the date first above written.

                                    NBT BANCORP INC.

                                    By:    /s/ Daryl R. Forsythe
                                        -------------------------------
                                    Name:  Daryl R. Forsythe

                                    Title: President and Chief Executive

                                           Officer

                                    BSB BANCORP, INC.

                                    By:    /s/ Thomas L. Thorn
                                        -------------------------------
                                    Name:  Thomas L. Thorn

                                    Title: Acting President and Chief Executive

                                           Officer



                                      - i -
<PAGE>   102

                                                                       EXHIBIT D

                              CERTIFICATE OF MERGER

                                BSB BANCORP, INC.

                                      INTO

                                NBT BANCORP INC.

                  Pursuant to Title 8, Section 251 of the General Corporation
Law of the State of Delaware, NBT Bancorp Inc., a corporation organized and
existing under the law of the State of Delaware ("NBT"), hereby certifies to the
following facts relating to the merger of BSB Bancorp, Inc., a corporation
organized and existing under the law of the State of Delaware ("BSB"), with and
into NBT:

                  FIRST:   The name and state of incorporation of each
constituent entity that is a party to the merger is as follows:

<TABLE>
<CAPTION>
                       Name                        State of Incorporation
                       ----                        ----------------------
                  <S>                              <C>
                  NBT Bancorp Inc.                         Delaware

                  BSB Bancorp, Inc.                        Delaware
</TABLE>

                  SECOND:  An Agreement and Plan of Merger, dated as of April
19, 2000, by and between NBT and BSB (the "Agreement and Plan of Merger"), has
been approved, adopted, certified, executed and acknowledged by each of the
constituent corporations in accordance with the requirements of Section 251 of
the General Corporation Law of the State of Delaware.

                                      - i -
<PAGE>   103

                  THIRD:   (a)      Pursuant to the Agreement and Plan of
Merger, the surviving corporation of the merger is NBT, a Delaware corporation
(the "Surviving Corporation"), and the name of the Surviving Corporation is
"____________".

                           (b)      Article FOURTH of the Certificate of
Incorporation of the Surviving Corporation is amended to read as follows:

                           "FOURTH: The total number of shares of all classes of
                           stock which the Corporation shall have the authority
                           to issue is One Hundred Five Million (105,000,000)
                           shares, consisting of One Hundred Million
                           (100,000,000) shares of Common Stock having a par
                           value of $.01 per share and Five Million (5,000,000)
                           shares of Preferred Stock having a par value of $.01
                           per share."

                  FOURTH:  At the "Effective Time" of the merger as defined
below, the certificate of incorporation of NBT shall become the certificate of
incorporation of the Surviving Corporation with the amendments described above,
until amended in accordance with the provisions of the General Corporation Law
of the State of Delaware. At the Effective Time, the bylaws of NBT shall become
the bylaws of the Surviving Corporation, until amended in accordance with the
certificate of incorporation of NBT and the General Corporation Law of the State
of Delaware. At the Effective Time, the directors of the Surviving Corporation
will be the following individuals: ________________________. At the Effective
Time, the officers of the Surviving Corporation shall be as set forth in Exhibit
E to the Agreement and Plan of Merger.

                  FIFTH:   The executed Agreement and Plan of Merger is on file
at the office of the Surviving Corporation at the following address:


                                     - ii -
<PAGE>   104

                                    -----------------
                                    56-68 Exchange Street
                                    Binghamton, New York 13902

                  SIXTH:   A copy of the Agreement and Plan of Merger will be
furnished by the Surviving Corporation, on request and without cost, to any
stockholder of any constituent corporation.

                            [SIGNATURE PAGE FOLLOWS]


                                    - iii -
<PAGE>   105


                  IN WITNESS WHEREOF, NBT has caused this Certificate of Merger
to be duly executed as of this __ day of _______, 2000, to be effective at _____
p.m. on _________  ___, 2000.


ATTEST                                 NBT BANCORP INC.

By:                                    By:
   ---------------------------            ---------------------------

Name:                                  Name:

Title:                                 Title:


                                     - iv -
<PAGE>   106

                                                                       EXHIBIT E

                            SENIOR EXECUTIVE OFFICERS

Daryl R. Forsythe          Chairman, President and Chief Executive Officer

William C. Craine          Vice Chairman

Joe C. Minor               Treasurer

Larry G. Denniston         Secretary


                                      - i -
<PAGE>   107

                                                                       EXHIBIT F

                                BSB BANCORP, INC.

                              STOCKHOLDER AGREEMENT

                  This STOCKHOLDER AGREEMENT, dated as of April 19, 2000, is
entered into by and among NBT Bancorp Inc., a Delaware corporation ("NBT"), and
the stockholders of BSB Bancorp, Inc., a Delaware corporation ("BSB"),
identified on Schedule I hereto (collectively, the "Stockholders"), who are
directors, executive officers or other affiliates of BSB (for purposes of Rule
145 under the Securities Act of 1933, as amended, and for purposes of qualifying
the Merger (defined below) for "pooling-of-interests" accounting treatment).

                  WHEREAS, NBT and BSB have entered into an Agreement and Plan
of Merger, dated as of April 19, 2000 (the "Agreement"), which is conditioned
upon the execution of this Stockholder Agreement and which provides for, among
other things, the merger of BSB with and into NBT, in a stock-for-stock
transaction (the "Merger"); and

                  WHEREAS, in order to induce NBT to enter into and consummate
the Agreement, each of the Stockholders agrees to, among other things, vote in
favor of the Agreement, the Merger and the other transactions contemplated by
the Agreement in his or her capacity as a stockholder of BSB;

                  NOW, THEREFORE in consideration of the premises, the mutual
covenants and agreements set forth herein and other good and valuable
consideration, the sufficiency of which is hereby acknowledged, the parties
hereto agree as follows:

         1.       OWNERSHIP OF BSB COMMON STOCK. Each Stockholder represents and
warrants that the number of shares of BSB common stock, par value $.01 per share
("BSB Common Stock"), set forth opposite such Stockholder's name on Schedule I
hereto is the total number of shares of BSB Common Stock over which such person
has "beneficial ownership" within the meaning of Rule 13d-3 under the Securities
Exchange Act of 1934, as amended, except that the provisions of Rule
13d-3(d)(1)(i) shall be considered without any limit as to time.

         2.       AGREEMENTS OF THE STOCKHOLDERS. Each Stockholder covenants and
agrees that:

                  (a)      Such Stockholder shall, at any meeting of the holders
of any or all classes or series of BSB Common Stock called for the purpose (or
in connection with any action taken by written consent), vote or cause to be
voted all shares of BSB Common Stock with respect to which such Stockholder has
voting power (including the power to vote or to direct the voting of) whether
owned as of the date hereof or hereafter acquired (the "Shares") in favor of the
Agreement, the Merger and the other transactions contemplated by the Agreement.
Notwithstanding the foregoing, or any other provision of this Stockholder
Agreement, NBT shall have no agreement, arrangement or understanding with any
Stockholder as to directing the voting of any shares of BSB Common Stock to the
extent it would result in NBT, individually or with any of its Affiliates (as
defined in the next

<PAGE>   108

sentence) or Associates (as defined in the next sentence) becoming the
Beneficial Owner (as defined in the next sentence) of five percent or more of
the Voting Stock (as defined in the next sentence) of BSB. The terms
"Affiliates," "Associates," "Beneficial Owner," and "Voting Stock" are as
defined or referenced in Article 14 of the BSB Certificate of Incorporation. In
determining which, if any, Stockholder that NBT shall have no agreement,
arrangement or understanding with as to directing the voting of any shares of
BSB Common Stock, reference shall be made to the Stockholders in order of the
amount of BSB Common Stock set forth opposite such Stockholder's name on
Schedule I hereto, beginning with the Stockholder who reports the fewest number
of shares, and continuing in ascending order therefrom.

                  (b)      Stockholder hereby agrees to timely deliver to NBT a
duly executed proxy in the form attached hereto as Exhibit A (the "Proxy"), such
Proxy to cover all of the Shares. In the event that Stockholder is unable to
provided any such Proxy in a timely manner, Stockholder hereby grants NBT a
power of attorney to execute and deliver such Proxy for and on behalf of
Stockholder, such power of attorney, which being coupled with an interest, shall
survive any death, disability, bankruptcy, or any other such impediment of
Stockholder. Upon execution of this Stockholder Agreement by Stockholder,
Stockholder hereby revokes any and all prior proxies or powers of attorney given
by Stockholder with respect to the Shares and agrees not grant any subsequent
proxies or powers of attorney with respect to the Shares until the earlier of
(i) such date and time as the Merger shall become effective in accordance with
the terms and provisions of the Agreement or (ii) the date of termination of
this Stockholder Agreement pursuant to Section 4 hereto.

                  (c)      Except as otherwise expressly permitted hereby, such
Stockholder shall not sell, pledge, transfer or otherwise dispose of his or her
shares of BSB Common Stock; provided, however, that this Section 2(c) shall not
apply to a pledge existing as of January 1, 2000.

                  (d)      Such Stockholder shall not in his or her capacity as
a stockholder of BSB directly or indirectly encourage or solicit, initiate or
hold discussions or negotiations with, or provide any information to, any
person, entity or group (other than NBT or an affiliate thereof) concerning any
merger, sale of all or substantially all of the assets or liabilities not in the
ordinary course of business, sale of shares of capital stock or similar
transaction involving BSB or otherwise inconsistent with the Agreement or the
transactions contemplated thereby. Nothing herein shall impair such
Stockholder's fiduciary obligations as a director of BSB.

                  (e)      Stockholder shall use his or her best efforts to take
or cause to be taken all action, and to do or cause to be done all things
necessary, proper or advisable under applicable laws and regulations to
consummate and make effective the Merger contemplated by the Agreement.

                  (f)      Such Stockholder shall not, prior to the public
release by NBT of an earnings report to its stockholders covering at least one
month of operations after consummation of the Merger (the "Restricted Period"),
sell, pledge (other than the replacement of a pledge existing on


                                      -2-
<PAGE>   109

January 1, 2000 of BSB Common Stock), transfer or otherwise dispose of the
shares of NBT common stock, par value $.01 per share (the "NBT Common Stock").

                  (g)      Such Stockholder shall comply with all applicable
federal and state securities laws in connection with any sale of NBT Common
Stock received in exchange for BSB Common Stock in the Merger, including the
trading and volume limitations as to sales by affiliates contained in Rule 145
under the Securities Act of 1933, as amended.

         3.       SUCCESSORS AND ASSIGNS. A Stockholder may sell, pledge,
transfer or otherwise dispose of his or her shares of BSB Common Stock only with
the prior written consent of NBT and if the acquirer of such BSB Common Stock
agrees in writing to be bound by this Stockholder Agreement.

         4.       TERMINATION. The parties agree and intend that this
Stockholder Agreement be a valid and binding agreement enforceable against the
parties hereto and that damages and other remedies at law for the breach of this
Stockholder Agreement are inadequate. This Stockholder Agreement may be
terminated at any time prior to the consummation of the Merger by the written
consent of the parties hereto and shall be automatically terminated in the event
that the Agreement is terminated in accordance with its terms; provided,
however, that if the holders of BSB Common Stock fail to approve the Agreement
or BSB fails to hold a stockholders' meeting to vote on the Agreement, then (i)
Section 2(a) clause (ii) hereof shall continue in effect as to any plan or
proposal received by BSB from any person, entity or group (other than NBT or any
affiliate thereof) prior to the termination of the Agreement or within 240 days
after such termination ("Plan or Proposal") and (ii) Section 2(c) hereof shall
continue in effect to preclude a sale (other than pursuant to normal brokers
transactions on the Nasdaq Stock Market), pledge (other than to a bona fide
financial institution or recognized securities dealer), transfer or other
disposition directly or indirectly to any such person, entity or group in
connection with any such Plan or Proposal, except upon consummation of such Plan
or Proposal.

         5.       NOTICES. Notices may be provided to NBT and the Stockholders
in the manner specified in the Agreement, with all notices to the Stockholders
being provided to them at the addresses set forth at Schedule I.

         6.       GOVERNING LAW. This Stockholder Agreement shall be governed by
the laws of the State of Delaware, without giving effect to the principles of
conflicts of laws thereof.

         7.       COUNTERPARTS. This Stockholder Agreement may be executed in
one or more counterparts, all of which shall be considered one and the same and
each of which shall be deemed an original.

         8.       HEADINGS. The Section headings contained herein are for
reference purposes only and shall not affect in any way the meaning or
interpretation of this Stockholder Agreement.


                                      -3-
<PAGE>   110

         9.       REGULATORY APPROVAL. If any provision of this Stockholder
Agreement requires the approval of any regulatory authority in order to be
enforceable, then such provision shall not be effective until such approval is
obtained; provided, however, that the foregoing shall not affect the
enforceability of any other provision of this Stockholder Agreement.

                             SIGNATURE PAGE FOLLOWS


                                      -4-
<PAGE>   111



                  IN WITNESS WHEREOF, NBT, by a duly authorized officer, and
each of the Stockholders have caused this Stockholder Agreement to be executed
and delivered as of the day and year first above written.

NBT BANCORP INC.

By:
    -------------------------------------
    Daryl R. Forsythe
    President and Chief Executive Officer

STOCKHOLDERS:

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

<PAGE>   112


                                   SCHEDULE I

                                                  Number of Shares of BSB Common

Name and Address of Stockholder                       Stock Beneficially Owned


<PAGE>   113



                                IRREVOCABLE PROXY

                                TO VOTE STOCK OF

                                BSB BANCORP, INC.

                  The undersigned stockholder of BSB Bancorp, Inc., a Delaware
corporation ("BSB"), hereby irrevocably (to the full extent permitted by the
Delaware General Corporation Law) appoints the members of the Board of Directors
of NBT Bancorp Inc., a Delaware corporation ("NBT"), and each of them, or any
other designee of NBT, as the sole and exclusive attorneys and proxies of the
undersigned, with full power of substitution and resubstitution, to vote and
exercise all voting and related rights (to the full extent that the undersigned
is entitled to do so) with respect to all of the shares of capital stock of BSB
that now are or hereafter may be beneficially owned by the undersigned, and any
and all other shares or securities of BSB issued or issuable in respect thereof
on or after the date hereof (collectively, the "Shares") in accordance with the
terms of this Irrevocable Proxy. The Shares beneficially owned by the
undersigned stockholder of BSB as of the date of this Irrevocable Proxy are
listed on the final page of this Irrevocable Proxy. Upon the undersigned's
execution of this Irrevocable Proxy, any and all prior proxies given by the
undersigned with respect to any Shares are hereby revoked and the undersigned
agrees not to grant any subsequent proxies with respect to the Shares until
after the Expiration Date (as defined below).

                  This Irrevocable Proxy is irrevocable (to the extent provided
in the Delaware General Corporation Law), is coupled with an interest,
including, but not limited to that certain Agreement and Plan of Merger dated as
of even date herewith by and between NBT and BSB ("Merger Agreement") and is
granted in consideration of NBT entering into the Merger Agreement for the
merger of BSB into NBT (the "Merger"). As used herein, the term "Expiration
Date" shall mean the earlier to occur of (i) such date and time as the Merger
shall become effective in accordance with the terms and provisions of the Merger
Agreement, and (ii) the date of termination of the Merger Agreement.

                  The attorneys and proxies named above, and each of them are
hereby authorized and empowered by the undersigned, at any time prior to the
Expiration Date, to act as the undersigned's attorney and proxy to vote the
Shares, and to exercise all voting and other rights of the undersigned with
respect to the Shares (including, without limitation, the power to execute and
deliver written consents pursuant to the Delaware General Corporation Law), at
every annual, special or adjourned meeting of the stockholders of BSB and in
every written consent in lieu of such meeting:

                  in favor of approval and adoption of the Merger Agreement and
                  of the transactions contemplated thereby.

                                      - i -
<PAGE>   114

                  The attorneys and proxies named above may not exercise this
Irrevocable Proxy on any other matter except as provided above. The undersigned
stockholder may vote the Shares on all other matters.

                  All authority herein conferred shall survive the death or
incapacity of the undersigned and any obligation of the undersigned hereunder
shall be binding upon the heirs, personal representatives, successors and
assigns of the undersigned.


                                     - ii -
<PAGE>   115


                  This Irrevocable Proxy shall terminate on, and be of no
further force or effect after, the Expiration Date.

                            (SIGNATURE PAGE FOLLOWS)


                                    - iii -
<PAGE>   116


                  This Irrevocable Proxy is coupled with an interest as
aforesaid and is irrevocable.

Dated:  April ___, 2000

                                           ------------------------------

                                           (Signature of Stockholder)



                                           ------------------------------

                                           (Print Name of Stockholder)



                                           Shares beneficially owned:


                                           ------------------------------


                       SIGNATURE PAGE TO IRREVOCABLE PROXY



                                     - iv -
<PAGE>   117

                                                                       EXHIBIT G

                                NBT BANCORP INC.

                              STOCKHOLDER AGREEMENT

         This STOCKHOLDER AGREEMENT, dated as of April 19, 2000, is entered into
by and among BSB Bancorp Inc., a Delaware corporation ("BSB"), and the
stockholders of NBT Bancorp Inc., a Delaware corporation ("NBT"), identified on
Schedule I hereto (collectively, the "Stockholders"), who are directors,
executive officers or other affiliates of NBT (for purposes of Rule 145 under
the Securities Act of 1933, as amended, and for purposes of qualifying the
Merger (defined below) for "pooling-of-interests" accounting treatment).

                  WHEREAS, NBT and BSB have entered into an Agreement and Plan
of Merger, dated as of April 19, 2000 (the "Agreement"), which is conditioned
upon the execution of this Stockholder Agreement and which provides for, among
other things, the merger of BSB with and into NBT, in a stock-for-stock
transaction (the "Merger"); and

                  WHEREAS, in order to induce BSB to enter into and consummate
the Agreement, each of the Stockholders agrees to, among other things, vote in
favor of the Agreement, the Merger and the other transactions contemplated by
the Agreement in his or her capacity as a stockholder of NBT;

                  NOW, THEREFORE in consideration of the premises, the mutual
covenants and agreements set forth herein and other good and valuable
consideration, the sufficiency of which is hereby acknowledged, the parties
hereto agree as follows:

         1.       OWNERSHIP OF NBT COMMON STOCK. Each Stockholder represents and
warrants that the number of shares of NBT common stock, par value $.01 per share
("NBT Common Stock"), set forth opposite such Stockholder's name on Schedule I
hereto is the total number of shares of NBT Common Stock over which such person
has "beneficial ownership" within the meaning of Rule 13d-3 under the Securities
Exchange Act of 1934, as amended, except that the provisions of Rule
13d-3(d)(1)(i) shall be considered without any limit as to time.

         2.       AGREEMENTS OF THE STOCKHOLDERS. Each Stockholder covenants and
agrees that:

                  (a)      Such Stockholder shall, at any meeting of the holders
of any or all classes or series of NBT Common Stock called for the purpose (or
in connection with any action taken by written consent), vote or cause to be
voted all shares of NBT Common Stock with respect to which such Stockholder has
voting power (including the power to vote or to direct the voting of) whether
owned as of the date hereof or hereafter acquired (the



<PAGE>   118

"Shares") in favor of the Agreement, the Merger and the other transactions
contemplated by the Agreement. Notwithstanding the foregoing, or any other
provision of this Stockholder Agreement, BSB shall have no agreement,
arrangement or understanding with any Stockholder as to directing the voting of
any shares of NBT Common Stock to the extent it would result in NBT,
individually or with any of its Affiliates (as defined in the next sentence) or
Associates (as defined in the next sentence) becoming the Beneficial Owner (as
defined in the next sentence) of five percent or more of the Voting Stock (as
defined in the next sentence) of NBT. The terms "Affiliates," "Associates,"
"Beneficial Owner," and "Voting Stock" are as defined or referenced in Article
11 of the NBT Certificate of Incorporation. In determining which, if any,
Stockholder that BSB shall have no agreement, arrangement or understanding with
as to directing the voting of any shares of NBT Common Stock, reference shall be
made to the Stockholders in order of the amount of NBT Common Stock set forth
opposite such Stockholder's name on Schedule I hereto, beginning with the
Stockholder who reports the fewest number of shares, and continuing in ascending
order therefrom.

                  (b)      Stockholder hereby agrees to timely deliver to BSB a
duly executed proxy in the form attached hereto as Exhibit A (the "Proxy"), such
Proxy to cover all of the Shares. In the event that Stockholder is unable to
provided any such Proxy in a timely manner, Stockholder hereby grants BSB a
power of attorney to execute and deliver such Proxy for and on behalf of
Stockholder, such power of attorney, which being coupled with an interest, shall
survive any death, disability, bankruptcy, or any other such impediment of
Stockholder. Upon execution of this Stockholder Agreement by Stockholder,
Stockholder hereby revokes any and all prior proxies or powers of attorney given
by Stockholder with respect to the Shares and agrees not grant any subsequent
proxies or powers of attorney with respect to the Shares until the earlier of
(i) such date and time as the Merger shall become effective in accordance with
the terms and provisions of the Agreement or (ii) the date of termination of
this Stockholder Agreement pursuant to Section 4 hereto.

                  (c)      Except as otherwise expressly permitted hereby, such
Stockholder shall not sell, pledge, transfer or otherwise dispose of his or her
shares of NBT Common Stock; provided, however, that this Section 2(c) shall not
apply to a pledge existing as of January 1, 2000.

                  (d)      Such Stockholder shall not in his or her capacity as
a stockholder of NBT directly or indirectly encourage or solicit, initiate or
hold discussions or negotiations with, or provide any information to, any
person, entity or group (other than BSB or an affiliate thereof) concerning any
merger, sale of all or substantially all of the assets or liabilities not in the
ordinary course of business, sale of shares of capital stock or similar



                                      -2-
<PAGE>   119

transaction involving NBT or otherwise inconsistent with the Agreement or the
transactions contemplated thereby. Nothing herein shall impair such
Stockholder's fiduciary obligations as a director of NBT.

                  (e)      Stockholder shall use his or her best efforts to take
or cause to be taken all action, and to do or cause to be done all things
necessary, proper or advisable under applicable laws and regulations to
consummate and make effective the Merger contemplated by the Agreement.

                  (f)      Such Stockholder shall not, prior to the public
release by NBT of an earnings report to its stockholders covering at least one
month of operations after consummation of the Merger (the "Restricted Period"),
sell, pledge (other than the replacement of a pledge existing on January 1, 2000
of NBT Common Stock), transfer or otherwise dispose of his or her shares of NBT
common stock, par value $.01 per share (the "NBT Common Stock").

         3.       SUCCESSORS AND ASSIGNS. A Stockholder may sell, pledge,
transfer or otherwise dispose of his or her shares of NBT Common Stock only with
the prior written consent of BSB and if the acquirer of such NBT Common Stock
agrees in writing to be bound by this Stockholder Agreement.

         4.       TERMINATION. The parties agree and intend that this
Stockholder Agreement be a valid and binding agreement enforceable against the
parties hereto and that damages and other remedies at law for the breach of this
Stockholder Agreement are inadequate. This Stockholder Agreement may be
terminated at any time prior to the consummation of the Merger by the written
consent of the parties hereto and shall be automatically terminated in the event
that the Agreement is terminated in accordance with its terms; provided,
however, that if the holders of NBT Common Stock fail to approve the Agreement
or NBT fails to hold a stockholders' meeting to vote on the Agreement, then (i)
Section 2(a) clause (ii) hereof shall continue in effect as to any plan or
proposal received by NBT from any person, entity or group (other than NBT
Bancorp or any affiliate thereof) prior to the termination of the Agreement or
within 240 days after such termination ("Plan or Proposal") and (ii) Section
2(c) hereof shall continue in effect to preclude a sale (other than pursuant to
normal brokers transactions on the Nasdaq Stock Market), pledge (other than to a
bona fide financial institution or recognized securities dealer), transfer or
other disposition directly or indirectly to any such person, entity or group in
connection with any such Plan or Proposal, except upon consummation of such Plan
or Proposal.


                                      -3-
<PAGE>   120

         5.       NOTICES. Notices may be provided to BSB and the Stockholders
in the manner specified in the Agreement, with all notices to the Stockholders
being provided to them at the addresses set forth at Schedule I.

         6.       GOVERNING LAW. This Stockholder Agreement shall be governed by
the laws of the State of Delaware, without giving effect to the principles of
conflicts of laws thereof.

         7.       COUNTERPARTS. This Stockholder Agreement may be executed in
one or more counterparts, all of which shall be considered one and the same and
each of which shall be deemed an original.

         8.       HEADINGS. The Section headings contained herein are for
reference purposes only and shall not affect in any way the meaning or
interpretation of this Stockholder Agreement.

         9.       REGULATORY APPROVAL. If any provision of this Stockholder
Agreement requires the approval of any regulatory authority in order to be
enforceable, then such provision shall not be effective until such approval is
obtained; provided, however, that the foregoing shall not affect the
enforceability of any other provision of this Stockholder Agreement.

                             SIGNATURE PAGE FOLLOWS


                                      -4-
<PAGE>   121


                  IN WITNESS WHEREOF, BSB, by a duly authorized officer, and
each of the Stockholders have caused this Stockholder Agreement to be executed
and delivered as of the day and year first above written.

BSB BANCORP, INC.

By:
   ---------------------------------


STOCKHOLDERS:

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

- ------------------------------------      ------------------------------------

<PAGE>   122

                                   SCHEDULE I

                                                  Number of Shares of NBT Common

Name and Address of Stockholder                       Stock Beneficially Owned


<PAGE>   123

                                IRREVOCABLE PROXY

                                TO VOTE STOCK OF

                                NBT BANCORP INC.

                  The undersigned stockholder of NBT Bancorp Inc., a Delaware
corporation ("NBT"), hereby irrevocably (to the full extent permitted by the
Delaware General Corporation Law) appoints the members of the Board of Directors
of BSB Bancorp, Inc., a Delaware corporation ("BSB"), and each of them, or any
other designee of BSB, as the sole and exclusive attorneys and proxies of the
undersigned, with full power of substitution and resubstitution, to vote and
exercise all voting and related rights (to the full extent that the undersigned
is entitled to do so) with respect to all of the shares of capital stock of NBT
that now are or hereafter may be beneficially owned by the undersigned, and any
and all other shares or securities of NBT issued or issuable in respect thereof
on or after the date hereof (collectively, the "Shares") in accordance with the
terms of this Irrevocable Proxy. The Shares beneficially owned by the
undersigned stockholder of NBT as of the date of this Irrevocable Proxy are
listed on the final page of this Irrevocable Proxy. Upon the undersigned's
execution of this Irrevocable Proxy, any and all prior proxies given by the
undersigned with respect to any Shares are hereby revoked and the undersigned
agrees not to grant any subsequent proxies with respect to the Shares until
after the Expiration Date (as defined below).

                  This Irrevocable Proxy is irrevocable (to the extent provided
in the Delaware General Corporation Law), is coupled with an interest,
including, but not limited to that certain Agreement and Plan of Merger dated as
of even date herewith by and between NBT and BSB ("Merger Agreement") and is
granted in consideration of BSB entering into the Merger Agreement for the
merger of BSB into NBT (the "Merger"). As used herein, the term "Expiration
Date" shall mean the earlier to occur of (i) such date and time as the Merger
shall become effective in accordance with the terms and provisions of the Merger
Agreement, and (ii) the date of termination of the Merger Agreement.

                  The attorneys and proxies named above, and each of them are
hereby authorized and empowered by the undersigned, at any time prior to the
Expiration Date, to act as the undersigned's attorney and proxy to vote the
Shares, and to exercise all voting and other rights of the undersigned with
respect to the Shares (including, without limitation, the power to execute and
deliver written consents pursuant to the Delaware


                                     - i -
<PAGE>   124

General Corporation Law), at
every annual, special or adjourned meeting of the stockholders of NBT and in
every written consent in lieu of such meeting:

                  in favor of approval and adoption of the Merger Agreement and
                  of the transactions contemplated thereby.

                  The attorneys and proxies named above may not exercise this
Irrevocable Proxy on any other matter except as provided above. The undersigned
stockholder may vote the Shares on all other matters.

                  All authority herein conferred shall survive the death or
incapacity of the undersigned and any obligation of the undersigned hereunder
shall be binding upon the heirs, personal representatives, successors and
assigns of the undersigned.


                                     - ii -
<PAGE>   125


                  This Irrevocable Proxy shall terminate on, and be of no
further force or effect after, the Expiration Date.


                                    (SIGNATURE PAGE FOLLOWS)


                                    - iii -
<PAGE>   126


                  This Irrevocable Proxy is coupled with an interest as
aforesaid and is irrevocable.

Dated:  April ___, 2000

                                                  ------------------------------

                                                  (Signature of Stockholder)



                                                  ------------------------------

                                                  (Print Name of Stockholder)



                                                  Shares beneficially owned:


                                                  ------------------------------

                       SIGNATURE PAGE TO IRREVOCABLE PROXY

                                     - iv -


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