Notwithstanding any contrary provision of general or special law, cities, towns and other political subdivisions of this state may enter into agreements to comply with federal tax and securities laws and may rebate to the United States Treasury from available sources, any income from investments (including gains from the disposition of investments) of proceeds of bonds or notes to the extent deemed necessary to exempt (in whole or in part) the interest paid on the bonds or notes from federal income taxation. The term of any such agreement may extend to a date six (6) years after the final maturity of the bonds or notes to which the agreement relates.