The governing body of any municipality having a population of over one hundred twenty thousand (120,000) and owning and operating a public utility or utilities, or any board of public utilities or managing board having the management and control of such utility or utilities is hereby authorized, permitted and empowered, at its option, to extend and provide for its employees, their dependents and survivors, the protection and benefits provided by the old age and survivors insurance system embodied in the social security act of congress approved August 14, 1935, Chapter 531, 49 Stat. 620, officially cited as the “social security act” (including regulations and requirements issued pursuant thereto) as such act has been and may from time to time be amended: Provided, That a majority of the employees in the public utility or utilities by secret written ballot, vote to be included under the provisions of the old age and survivors insurance system of congress which referendum shall be conducted as provided in said federal law by the governor or any agency or individual designated by the governor.