Mass. Gen. Laws ch. 164, § 47D

A municipal lighting plant created pursuant to the provisions of this chapter or any special law shall be exempt from the public record requirements of section 10 of chapter 66 and the open meeting requirements of sections 20 and 21 of chapter 30A in those instances when necessary for protecting trade secrets, confidential, competitively sensitive or other proprietary information provided in the course of proceedings conducted pursuant to this chapter when such municipal lighting plant board determines that such disclosure will adversely affect its ability to conduct business in relation to other entities making, selling, or distributing electric power and energy pursuant to this chapter.