Mich. Comp. Laws § 123.338

Sec. 8. After all outstanding bonds have been paid or their priority secured as aforesaid, or have been retired by the issue of separate refunding bonds, by the several public corporations, jointly or severally, or by the assumption by each of its proportion thereof, any public corporation shall have the right to take over the ownership and operation of that part of the system lying within its boundaries and the collection and disposition of the revenues derived therefrom, subject to such conditions as will secure to all the subdivisions the connections, flowage rights and other facilities necessary to the operation of their respective systems.