Mass. Gen. Laws ch. 6C § 46
In addition to any other power the department may have to enter into leases, the department may lease, at 1 time or from time to time, for terms not to exceed 99 years, upon such terms and conditions as the department in its discretion deems advisable, air rights over land owned or held by the department in connection with the turnpike and the Boston extension portion of the metropolitan highway system, including rights for support, access, utilities, light and air for such purposes as, in the opinion of the department, shall not impair the construction, full use, safety, maintenance, repair, operation or revenues of the turnpike or the metropolitan highway system but any such lease for a period of 40 years or more shall be subject to the approval of the governor. Any lease granted under this section may, with the consent of the department, be assigned, pledged or mortgaged and the lien of such pledge or mortgage may be foreclosed by appropriate action.
The department shall not lease any air rights in a particular location unless it shall find that the construction and use of buildings or other things to be erected or affixed pursuant to any such lease shall be in no way detrimental to the maintenance, use and operation of the turnpike or the metropolitan highway system and, in the city of Boston, unless the department shall also find, after consultation with the mayor of said city of Boston, that the construction and use of such buildings or other things shall preserve and increase the amenities of the community.
The construction or occupancy of any building or other thing erected or affixed under any lease under this section of air rights shall be subject to the building, fire, garage, health and zoning laws and the building, fire, garage, health and zoning ordinances, by-laws, rules and regulations applicable in the city or town in which such building or other thing is located.
A copy of all leases granted by the department under this section shall be filed by the department with the governor and with the mayor or chairperson of the board of selectmen of the respective city or town and such leases shall be deemed to be public records within the meaning of section 10 of chapter sixty-six.
Neither such air rights nor any buildings or other things erected or affixed pursuant to any such lease nor the proceeds from any such lease shall be taxed or assessed to the department under any general or special law; provided, however, that buildings and other things erected or affixed pursuant to any such lease 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; provided, further, that no part of the value of the land shall be included in any such assessment; and provided, further, that payment of any such taxes shall not be enforced by a lien upon or sale or taking of such land except that the leasehold estate may be sold or taken by the collector of taxes of the city or town wherein such real estate is situated for the nonpayment of any tax assessed as aforesaid in the manner provided by law for the sale or taking of real estate for nonpayment of local taxes. Such collector shall have, for the collection of taxes assessed under this section, all other remedies provided by the General Laws for the collection of taxes by collectors of cities and towns.
The department shall include in any lease of such air rights a provision whereby the lessee agrees, in the event that the foregoing tax provision is determined by any court of competent jurisdiction to be inapplicable, to pay annually to the city or town wherein such building or other thing leased is located, a sum of money in lieu of taxes which would otherwise be assessed for such year.
Mass. Gen. Laws ch. 6C, § 46