Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 40, § 22E

Whenever the board or officer having charge of a structure or facility owned by a city or town, and not within the limits of playgrounds or lands held for park, conservation or similar purposes whether acquired under general or special law and irrespective of the date of acquisition, determines that the whole or any part of the airspace above such structure or facility is not required for the purposes thereof, such board or officer shall publish once a week for at least three consecutive weeks in a newspaper of general circulation in such city or town an advertisement of such determination, identifying the structure or facility involved. Such advertisement shall invite sealed proposals for the leasing of such airspace for a term not exceeding ninety-nine years and for the construction of a building therein pursuant to basic drawings and outline specifications to be submitted with such proposal. Such advertisement shall also fix a time, not less than three months after the first publication of such advertisement, and specify a place, at which time and place such board or officer shall publicly open and read such sealed proposals.

Any provision of general or special law to the contrary notwithstanding, the city manager in the case of a city having a Plan D or Plan E charter, when authorized thereto by an affirmative vote of a majority of the city council, the mayor in the case of any other city, when authorized thereto by majority vote of the city council, and the selectmen in the case of a town, when authorized thereto by vote of the town at a town meeting, may lease, in accordance with whichever of the proposals so submitted is deemed most advantageous to such city or town, the whole or any part of the airspace determined as aforesaid to be not required for the purposes of such structure or facility and such parts of such structure or facility or the site thereof as may be necessary for structural supports and means of ingress and egress to and from the building to be erected in such airspace. Buildings and other things erected or affixed pursuant to the lease of any such airspace shall be taxed to the lessee thereof or his assigns in the same manner and to the same extent as if such lessee or his assigns were the owners of the land in fee and the value of the land shall be included in any such assessment.