Neb. Rev. Stat. § 3-221

All powers, rights and authority granted to any municipality in sections 3-201 to 3-238 and 18-1502 may be exercised and enjoyed by two or more municipalities, or by this state and one or more municipalities therein, acting jointly, either within or without the territorial limits of either or any of said municipalities and within or without this state, or by this state or any municipality therein, acting jointly with any other state or municipality therein, either within or without this state, if the laws of such other state permit such joint action.