(1) For the purposes of this part, unless otherwise qualified: “Governing body” includes the commissioners of an authority, the governing body of a municipality and the head of an agency of a state or the United States if the public agency is other than an authority or municipality; and
(2) “Public agency” includes municipality and authority, each as defined in this chapter, any agency of the state government and of the United States, and any municipality, political subdivision and agency of an adjoining state.
(3) All powers, privileges and authority granted by this chapter may be exercised and enjoyed by an authority jointly with any public agency of this state, and jointly with any public agency of any adjoining state or of the United States to the extent that the laws of the other state or of the United States permit such joint exercise of enjoyment.
(4) Any agency of the state government, when acting jointly with any authority, may exercise and enjoy all the powers, privileges and authority conferred by this chapter upon an authority.