Section 9. The real estate and tangible personal property of the corporation 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, the municipality may determine a sum to be paid to it 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 then 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.

The municipality may, however, agree with the corporation upon the payments to be made, or the corporation may make and the municipality 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 act 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 the corporation for an economic development project and sold by it, or the taxation to the same extent and in the same manner as real estate of the commonwealth is taxed, of real estate so acquired by the corporation and leased by it; provided, however, that real estate so acquired by the corporation and sold or leased to an urban redevelopment corporation or other entity operating under chapter one hundred 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.

The corporation and the debentures, revenue bonds and revenue refunding bonds issued under the provisions of this act, their transfer and the income therefrom including any profit made on the sale thereof, shall at all times be free from taxation by the commonwealth or any subdivision thereof.