N.J. Stat. § 40:23-14
The board of chosen freeholders of any county may by contract, join with the governing body of any municipality within the county or adjoining it, or of any other county or of any district, to acquire or construct any public improvement or works, do any act, maintain any department or render any service which any such municipality, county or district may acquire, construct, do, maintain or render, but no county under any such contract may acquire, construct, maintain or operate any property or service defined as a "public utility" by section 48:2-13 of the title Public Utilities, until a majority of the legal voters in the county affected shall, at an election advertised, held and conducted in accordance with the general laws relating to elections, vote in favor of a proposition to be submitted in the manner provided in section 40:23-15 of this title.
N.J.S. § 40:23-14