Whenever the governing bodies of two or more cities or counties consolidate their existing public library services, as a joint exercise of powers under Chapter 5 (commencing with Section 6500), Division 7, Title 1 of the Government Code, and the ownership or management of the cities’ and counties’ library facilities and other library assets are turned over to a newly formed joint agency, any boards of public library trustees existing prior to the consolidation, may be dissolved by ordinance.