Section 15B. A town, city, or district authorized to furnish water for domestic purposes, may, with the advice and approval of the state department of environmental protection, sell at public or private sale, or may exchange any real property, or any easements, whether taken by eminent domain or otherwise, no longer needed for public water supply works under its charge, or may from time to time lease any property not then so needed, or may permit the use thereof by the public for recreational purposes; and may in its discretion, by lease, license or other agreement, permit the construction and maintenance on any land under its control of towers, poles, wires, and other structures for the purpose of transmitting electric power over lands and water held for water supply purposes; provided, that such lease, license or agreement will not, in the opinion of the said department, affect or interfere with the water supply; and provided, further, that said city, town or district may, with the approval of said department, revoke said lease, license or agreement for cause to be determined by it.

No land acquired by eminent domain by a city or town within the limits of another city or town, and no land of a district so acquired, may be sold or exchanged pursuant to this section unless it is offered to be conveyed to the city or town wherein it lies for a minimum amount, specified by vote of the city council or a town or district meeting, for which the city, town or district owning it is willing to sell it, nor unless such offer is not accepted within six months after notice thereof is given to the mayor or selectman of the city or town wherein such land lies, nor unless such conveyance is made within three months after the expiration of such six months.