The authority of any public waterworks or water service owned or furnished by any city, town, water district, fire district, or any other municipal or quasi-municipal corporation to enter into contracts with each other for the sale of water at wholesale is hereby confirmed, and the wholesale contracts shall be exempt from the provisions of § 39-3-24(1) but shall be filed with the division; provided, however, that whenever any public waterworks or water service owned or furnished by any city, town, water district, fire district, or any other municipal or quasi-municipal corporation shall enter into wholesale contracts with each other, the fair wholesale rates or charges for the quantity of water taken shall be for such times and at such rates fixed to continue during such periods as may be mutually agreed upon, or in default of agreement, as shall be determined by the commission in accordance with the provisions of § 39-3-10 and § 39-3-11.