The legislature, by act enacted by an affirmative vote of two-thirds of the members to which each house is entitled, may authorize the issuance of refunding special purpose revenue bonds for the purpose of refunding any special purpose revenue bonds then outstanding and issued under this part, whether or not such outstanding special purpose revenue bonds have matured or are then subject to redemption. The legislature is further authorized to provide, by act finally enacted by an affirmative vote of two-thirds of the members to which each house is entitled, for the issuance of a single issue of special purpose revenue bonds for the combined purposes of (1) financing or refinancing the cost of a project or improvement or expansion thereof, and (2) refunding special purpose revenue bonds which shall theretofore have been issued under this part and shall then be outstanding, whether or not such outstanding special purpose revenue bonds have matured or are then subject to redemption. Nothing in this section shall require or be deemed to require the legislature to elect to redeem or prepay special purpose revenue bonds being refunded, or to redeem or prepay special purpose revenue bonds being refunded which were issued in the form customarily known as term bonds in accordance with any sinking fund installment schedule specified in any law authorizing the issuance thereof, or, in the event the department elects to redeem or prepay any such bonds, to redeem or prepay as of any particular date or dates. The issuance of such special purpose revenue bonds, the maturities and other details thereof, and the rights and remedies of the holders thereof, and the rights, powers, privileges, duties, and obligations of the department with respect to the same, shall be governed by the foregoing provisions of this part insofar as the same may be applicable.