Mass. Gen. Laws ch. 164 § 9
An electric company which owns or operates an hydro-electric plant may, subject to all laws governing the issue of capital stock by electric companies, issue preferred stock of one or more classes to such amount, not exceeding twice the amount of the general or common stock then outstanding, as the department may from time to time approve; and, in approving, under section fourteen, the issue of stock or bonds by an hydro-electric company which has theretofore issued and has outstanding stock or bonds for which the approval of the department or its predecessors was not required, the department may direct that such new stock or bonds shall bear some distinctive designation. An electric company may, with the consent of the department and to such extent and upon such terms as the department may approve, acquire the stocks, bonds or other obligations of a corporation, association or person owning a storage reservoir in the states of Vermont or New Hampshire, the operation of which will be beneficial to an hydro-electric plant in this commonwealth owned by such company, or owning an electric system completed or under construction in another state from which such electric company derives or has contracted for an amount of electrical energy which in the opinion of the department is a substantial amount.
Mass. Gen. Laws ch. 164, § 9