Any public body may issue refunding bonds for the purpose of refunding all or any part of its revenue bonds now or hereafter outstanding, whether or not such revenue bonds are at the time of the refunding due or optional for redemption, under the circumstances and restrictions set forth in this article. Refunding bonds shall be payable from revenues derived from the same enterprise as the revenue bonds to be refunded except where the public body has outstanding revenue bonds payable from the revenues of an enterprise and is authorized under any other law to combine and consolidate such enterprise with another enterprise and issue revenue bonds payable from the revenues of the combined and consolidated enterprises. An issue of refunding bonds may refund part or all of one or more issues of outstanding revenue bonds: Provided, That part or all of two or more issues of outstanding revenue bonds may not be refunded under this article unless either (a) all of the issues of outstanding revenue bonds to be refunded are payable from revenues derived from the same enterprise, or (b) the public body is authorized under any other law to combine or consolidate the enterprises in question and issue revenue bonds payable from the revenues of the combined or consolidated enterprises.

Refunding bonds may be issued hereunder whenever the governing body of the public body deems it expedient and, notwithstanding any provision in this article to the contrary, may be issued as part of a series of revenue bonds issued for the purpose, in addition to such refunding, of financing the acquisition or construction of improvements, betterments, extensions or replacements to the particular enterprise, as provided by other articles of this code.