Any mortgage granted under this Sub-part may be foreclosed by seizure and sale of the encumbered property, in the manner provided by law for the foreclosure of conventional mortgages, including the right to executory process.  

Any resolution adopted or mortgage or trust indenture entered into under the provisions of this Sub-part shall provide for the granting by the governing authority of the parish of a franchise to the purchaser at foreclosure sale for the operation of the bridge mortgaged or indentured.  This franchise shall run for a period of not more than forty years from the date of the sale and shall be subject to any other constitutional or statutory limitations pertaining to the granting of municipal franchises.