Section 15. Any city or town which is a member of an authority may place upon the official ballot at any biennial or regular or special city election or annual or special town election the following question:
''Shall this (city, town) continue to be a member of the (name) (name) Regional Transit Authority?''
Such question shall not be placed upon the official ballot unless the city council or town meeting shall have voted that such question be so placed, or a petition signed by not less than five per cent of the registered voters of the city or town, certified as such by the registrars of voters thereof, shall have been filed with the city or town clerk, at least sixty days before the date for any such election. Forms for such petitions shall be made available without cost by the city or town clerk and each form shall bear the following heading: ''The undersigned registered voters of the (city or town) hereby petition for the placement upon the official ballot of the question whether this (city, town) shall continue to be a member of the (name) Regional Transit Authority''.
The votes upon such a question shall be counted and returned to the city or town clerk in the same manner as votes for candidates in municipal elections. Said clerk shall forthwith notify the authority of the result of the vote. If a majority of the votes cast upon the question shall be in the negative, the authority shall forthwith take all steps necessary and appropriate for the termination of membership of such city or town in such authority.