Mass. Gen. Laws ch. 32 § 2
The state employees' retirement system, the teachers' retirement system and all county, city and town contributory retirement systems, established under the provisions of this chapter, as existing on December thirty-first, nineteen hundred and forty-five, shall, subject to the provisions of sections one to twenty-eight inclusive, continue in operation with all the rights, properties, privileges and powers and subject to all the duties and liabilities accrued or potential now existing or hereafter created or granted. Subject to said sections, all rights and interests of any employee, beneficiary or member in any such system or in the assets thereof or in or to any annuity, pension or retirement allowance in effect on December thirty-first, nineteen hundred and forty-five, are hereby continued in full force. Each such system shall comprise the members, beneficiaries, officers, employees and, subject to said sections, properties which now or hereafter from time to time belong to it, and shall have all the powers necessary to effectuate the provisions of said sections. Subject to said sections, an employee of the commonwealth or the metropolitan district commission, the Massachusetts State College Building Authority, the University of Lowell Building Authority, the Massachusetts Parking Authority, the Old Colony Planning Council or the Boston Arena Authority shall be included in the state employees' retirement system, except that a register of probate shall be included in the system of the county in which he is elected, a teacher, as defined in section one, shall be included in the teachers' retirement system, except that a teacher employed by the school committee of the city of Boston shall be included in the State-Boston retirement system, an employee of a county or of a hospital district, an employee of a mosquito control district or a mosquito control project located within a county shall be included in the system of such county, an employee of a city or town other than a teacher as defined in section one shall be included in the system of or which pertains to the municipality by which he is employed, an employee of the Massachusetts Turnpike Authority shall be included in the Massachusetts Department of Transportation employees' retirement system, an employee of the police department of the Massachusetts Bay Transportation Authority shall be included in the Massachusetts Bay Transportation Authority police retirement system, an employee of the Massachusetts Housing Finance Agency shall be included in the Massachusetts Housing Finance Agency employees' retirement system, an employee of the Massachusetts Port Authority shall be included in the Massachusetts Port Authority employees' retirement system, an employee of the Greater Lawrence Sanitary District shall be included in the Greater Lawrence Sanitary District employees' retirement system, an employee of the Blue Hills Regional Vocational School system shall be included in the Blue Hills Regional Vocational School employees' retirement system, and an employee of the Minuteman Regional Vocational Technical School District shall be included in the Minuteman Regional Vocational Technical School District employees' retirement system, and an employee of a district shall be included in a system as provided for in subdivision (4) of section twenty-eight, except that in the case of a district which comprises cities and towns located in more than one county, or in the case of a district in which the cities and towns comprising such district may vary from time to time, the employees of such district may become members of the state employees' retirement system, subject to the provisions of subdivision (4) of section twenty-eight. Sections one to twenty-eight inclusive, to the fullest extent conformable to the terms thereof, shall be construed as a continuation of and amendment of sections one to thirty-eight A inclusive, sixty-eight A, sixty-eight B and sixty-eight C of chapter thirty-two, as in effect on December thirty-first, nineteen hundred and forty-five, and not as a new enactment. All orders, rules and regulations of any retirement board of any such system in force and effect on December thirty-first, nineteen hundred and forty-five, shall, except so far as inconsistent with said sections one to twenty-eight inclusive, remain in force until revoked or repealed.
No provision of this section shall operate so as to provide membership in any system established under this chapter for any employees of any district which is included in any agreement providing social security coverage for the employees of such district under the provisions of chapter one hundred and eighteen C.
Mass. Gen. Laws ch. 32, § 2