When any municipal or private corporation, engaged in providing or authorized to provide a water supply for any town, city or borough, deems it necessary that any public highway or part thereof shall be discontinued or altered in order to enable it to construct or enlarge a reservoir or to promote or carry out its authorized purposes in other respects in providing a pure and ample supply of water, it may apply to the selectmen of any town in which such part of such highway is located for such discontinuance or alteration. Such municipal or private corporation shall give twelve days’ notice of such application by publication in a newspaper published in the town or towns where such highways are located, and shall file, twelve days before such application, with the town clerk, a map showing the highways to be discontinued or altered. If such selectmen or any town denies such application or declines for thirty days to act upon it, such municipal or private corporation may petition the superior court for the judicial district in which such town is located, setting forth the facts in relation thereto and that such discontinuance or alteration is a matter of public convenience and necessity.