Mass. Gen. Laws ch. 164 § 94F
In connection with any investigation by the department concerning the rates, prices and charges made by a gas company, the department may take into consideration the rates, charges, classifications and schedules on file with the Federal Power Commission whereby the cost of gas purchased or received by such gas company is fixed and determined. If, while such investigation is pending before the department, a proceeding shall be instituted or be pending before the Federal Power Commission or an appeal therefrom to any court having jurisdiction, with respect to or affecting the cost of gas payable by such gas company, the department shall consider as an item of operating expense to said gas company the cost of gas set forth in rates, charges, classifications and schedules on file with the Federal Power Commission. If the cost of gas payable by said gas company shall be reduced by the official order of the Federal Power Commission or by official decree of the court, if appealed thereto, and the department shall have entered an order approving rates of said gas company based upon the cost of gas set forth in the rates, charges, classifications and schedules on file with the Federal Power Commission which were later reduced as above set forth, the department, upon its own motion or upon complaint and after notice and hearing, may order said gas company to refund to its customers any sums refunded to said gas company for the period subsequent to the effective date of the order of the department approving rates for the gas company as above set forth and may impose such restrictions, limitations, terms and conditions in such order as are considered necessary by it. The department may also make such order, upon its own motion or upon complaint and after due notice and hearing, in any case where the Federal Power Commission has ordered and a gas company has received a refund from a natural gas pipe line company as defined in this chapter.
Mass. Gen. Laws ch. 164, § 94F