Mass. Gen. Laws ch. 121C § 7
Except as provided herein rents and charges for services or facilities furnished or supplied by the corporation shall not be subject to supervision or regulation by any department, division, commission, board, bureau or agency of the commonwealth or any political subdivision thereof, and, if derived from a project in connection with which revenue bonds have been issued, shall, with all other revenues derived from the project, except such part thereof as may be necessary to pay such cost of maintenance, repair and operation and to provide such reserves therefor as may be provided for in the resolution authorizing the issuance of the bonds or in the trust agreement, but including such part thereof as may be necessary to provide such reserves for the payment of the principal of and the interest on said revenue bonds as may be provided for in such resolution or trust agreement, and including also the proceeds of any and all sales by the corporation of property within the project area, be set aside at such regular intervals as may be provided for in such resolution or trust agreement, in a sinking fund which is hereby pledged to and charged with the payment of (1) the interest upon such bonds as such interest shall fall due, (2) the principal of the bonds as the same shall fall due, (3) the necessary charges of paying agents for paying principal and interest, and (4) the redemption price or the purchase price of bonds retired by call or purchase as therein provided.
Mass. Gen. Laws ch. 121C, § 7