If off-street parking lots or structures are essential to the principal shopping district project, if 1 or more off-street parking lots or structures are already owned by the local governmental unit and were acquired through the issuance of revenue bonds, and if the remaining parking lots or structures are to be financed in whole or in part by special assessments and special assessment bonds, then the local governmental unit, to place all parking lots or structures on the same basis, may include as a part of the cost of parking lots or structures for the project the amount necessary to retire all or any part of the outstanding revenue bonds, inclusive of any premium not exceeding 5% necessary to be paid upon the redemption or purchase of those outstanding bonds. From the proceeds of the special assessments or from the sale of bonds issued in anticipation of the payment of the special assessments, the local governmental unit shall retire by redemption or purchase the outstanding revenue bonds. This section does not authorize the refunding of noncallable bonds without the consent of the holders of the bonds.