Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 92, § 86

Whenever, by reason of a taking by the commonwealth through the department for reservation or boulevard purposes under section 80, a public way is so affected that the public rights therein might otherwise be abridged, either by being wholly or partly included within the taking, any and all exceptions and reservations made in said taking in favor of any municipality within which said way or part thereof lies, and of the public, and of persons, shall be valid, effectual and binding; and in order to insure to the parties concerned the full and perfect enjoyment of the uses thereby reserved the department may make grants of or convey easements, enter into agreements, issue licenses, and generally conclude arrangements to that end; but no such grant, agreement, license or arrangement shall be taken or held to abrogate or abridge the control of the department over the land included in said taking except as in said exceptions and reservations provided, or the right of the department to make rules and regulations for the government and use of any boulevard or crossway which may be laid out and maintained over said land or over any portion thereof, not inconsistent with such exceptions and reservations.