Section 16. The real estate and tangible personal property of an operating agency including houses constructed by a housing authority on private land in rural areas under the provisions of section twenty-seven shall be deemed to be public property used for essential public and governmental purposes and shall be exempt from taxation and from betterments and special assessments; provided, that in lieu of such taxes, betterments and special assessments, a city or town in which an operating agency holds real estate used or to be used in connection with such a project may determine a sum to be paid to the city or town annually in any year or period of years, such sum to be in any year not in excess of the amount that would be levied at the current tax rate upon the average of the assessed value of such real estate, including buildings and other structures, for the three years preceding the year of acquisition thereof, the valuation for each year being reduced by all abatements thereon.

Whenever a city or town in which such real estate is located shall have made a general revaluation or reassessment of its real property for purposes of taxation, the valuation of such real estate shall be determined by the assessors of said city or town as of January first, in the year succeeding such revaluation or reassessment, by dividing the amount of the payment authorized by this section for the year last preceding the revaluation by the residential class tax rate of said city or town for the year of the revaluation, so that the payment with respect to such land shall remain substantially the same as that made prior to such revaluation or reassessment. The operating agency, if aggrieved by the determination of the assessors, may within six months after written notice thereof appeal to the appellate tax board.

Such a city or town may, however, agree with such an operating agency upon the payments to be made to the city or town as herein provided or such agency may make and such city or town may accept such payments, the amount of which shall not in either case be subject to the foregoing limitation. The last paragraph of section six and all of section seven of chapter fifty-nine shall, so far as apt, be applicable to payments under this section.

Nothing in this chapter shall be construed to prevent the taxation to the same extent and in the same manner as other real estate is taxed, of real estate acquired by an operating agency for an urban renewal project and sold by it, or of the leasehold interests and buildings and other structures belonging to private individuals or corporations on land acquired by it; provided, however, that real estate so acquired by an operating agency and sold or leased to an urban redevelopment corporation or other entity operating under chapter one hundred and twenty-one A, or to an insurance company or savings bank or group of savings banks operating under said chapter, shall be taxed as provided in said chapter and not otherwise; and provided, further, that nothing in this chapter or in chapter fifty-nine shall be construed to require a city or town to impose a tax on the leasehold of real estate owned by an operating agency and leased by it beyond any amount which the city or town and the operating agency have agreed to be the payment in lieu of taxes hereunder.