Any city, village or incorporated town which has heretofore entered into an agreement with the Federal government or any agency thereof for the construction, extension, improvement or repair of streets, or of a sewerage system or water system with the aid of a Federal grant, may, for the purpose of raising its portion of the funds necessary for such construction, extension, improvement or repair, provide a special tax or special assessment of the property benefited, and to anticipate the collection of such special tax or special assessment, or any installment thereof, may issue bonds, payable out of such special tax or special assessment, bearing interest at a rate not more than the maximum rate authorized by the Bond Authorization Act, as amended at the time of the making of the contract, nor less than 3 1/2% per annum.
     With respect to instruments for the payment of money issued under this Section either before, on, or after the effective date of this amendatory Act of 1989, it is and always has been the intention of the General Assembly (i) that the Omnibus Bond Acts are and always have been supplementary grants of power to issue instruments in accordance with the Omnibus Bond Acts, regardless of any provision of this Act that may appear to be or to have been more restrictive than those Acts, (ii) that the provisions of this Section are not a limitation on the supplementary authority granted by the Omnibus Bond Acts, and (iii) that instruments issued under this Section within the supplementary authority granted by the Omnibus Bond Acts are not invalid because of any provision of this Act that may appear to be or to have been more restrictive than those Acts.