The mayor and council of a city, the selectboard of a town, or the trustees of a village may negotiate and agree with the utility upon the price to be paid for the plant and property. However, any agreement shall not be binding upon any municipality until ratified by three-fifths of the voters present and voting by Australian ballot at a duly warned annual or special meeting which is preceded by at least 20 days by a public hearing on ratification of the agreement. Notice of the public hearing shall be given in the same manner as it is given for the annual meeting. A ratifying vote shall be had within six months from the date of the filing of the reply provided in section 2907 of this title. (Amended 1979, No. 183 (Adj. Sess.), § 3.)