Any two or more municipalities may enter into and revise from time to time, and may fulfill, contracts jointly to acquire, construct or operate all or any part of a sewerage system. Any such agreement shall particularize (a) the portion or portions of the sewerage system to be jointly acquired, constructed or operated, (b) the acts relating to acquiring, constructing or operating such portion or portions of the sewerage system to be performed jointly by the municipalities and (c) the method of apportioning the cost thereof. Whenever any two or more municipalities have entered into such an agreement, the sewer authorities of such municipalities jointly shall have, for the portion or portions of the sewerage system and for the acts relating to acquisition, construction or operation of the sewerage system covered by the agreement, all of the authority conferred by this chapter on a municipality and each such municipality shall continue to have all other authority conferred by this chapter.