(a) Any city of the first class having a city manager form of government and divided by a state line shall have the authority to join in the purchase, construction, and operation of a sewage system with the adjoining city in another state for each of the municipalities, and to execute an agreement for the joint obligation of the municipalities and secure the payment thereof by a joint pledge of the net revenues derived from the operation of the sewage systems.
(b) The municipalities shall employ a joint manager for the operation of the sewage system who shall be hired by the city managers of the municipalities and who shall serve under the direct supervision of the city managers jointly.