Notwithstanding any other provisions of this chapter, the board of supervisors, upon its own motion or upon receipt of a petition signed by 20 or more taxpayers of an existing lighting maintenance district asking for the installation and maintenance of additional lights, may, by order entered upon its minutes, make the expenses of the installation and maintenance of the additional lights a charge upon the existing district if the board determines that it will be just and equitable, and in the public interest for the additional cost, if any, to be paid by the district as a whole. If sufficient funds are available or will be available from a tax levy already made or after the tax levy has been made, the board may proceed with the installation of the additional lights.