Mass. Gen. Laws ch. 90 § 9B
The provisions of this chapter relative to the registration of motor vehicles and the display of number plates shall not apply to motor vehicles having registrations and displaying plates issued by the armed forces of the United States in foreign countries for vehicles owned by military personnel, but said exemption shall be in effect for a period of only thirty days after the owner thereof has entered the commonwealth for the purpose of traveling either to his place of residence or to a point of military duty nor shall this chapter apply to such registration and display of number plates on fire apparatus or marked police vehicles from any one of the states of Maine, New Hampshire, Vermont, Rhode Island, Connecticut and New York providing that the state from which such fire apparatus or marked police vehicle comes does not require the registration of and the display of number plates on such apparatus or vehicle.
Mass. Gen. Laws ch. 90, § 9B