Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 161B, § 3

Any city or town, or group or combination of cities or towns, other than a city or town included in the Massachusetts Bay Transportation Authority in which the Authority operates a fixed bus service, may, upon compliance with this section and with the approval of a city manager in the case of a city under a Plan E form of government, the mayor and city council in the case of all other cities, or the board of selectmen in the case of a town, be made into a body politic and corporate and a political subdivision of the commonwealth under the name of the municipality within the new authority having the greatest population, or under any other appropriate regional name agreed to by a majority of the member municipalities, and followed by the words “Transit Authority”.

Any such authority shall be deemed to be established upon written notification to the governor that the member municipalities have voted to establish a regional transit authority. Having so notified the governor, the advisory board established pursuant to section five shall proceed to appoint an administrator in accordance with section four. Once established, each such authority shall have the same powers, limitations, duties and organization as an authority established pursuant to section fourteen and shall in all respects be subject to the provisions of this chapter, except section fourteen, as if it were an authority so established.

Any city or town, or group or combination of cities or towns, other than a city or town included in the Massachusetts Bay Transportation Authority in which the Authority operates fixed route bus service may, with the approval of a city manager in the case of a city under a Plan E form of government, the mayor and city council in the case of all other cities or the board of selectmen in the case of a town and subject to the approval of the advisory board to a regional transit authority, join an authority which is not separated from the city or town or group or combination of cities and towns by more than 1 other municipality.

Notwithstanding any general or special law to the contrary, a city or town that is a member of an authority may, with the approval of the city manager in the case of a city under a Plan E form of government, the mayor and city council in the case of all other cities or the board of selectmen in the case of a town, join an additional authority, subject to the approval of the advisory board of the additional authority and provided that the city or town adjoins a city or town that is a member of the additional authority.