In order to place the Board upon a fair basis for making such contracts and for receiving bids for the sale of such power, it is expressly authorized, either from appropriations made by Congress or from funds secured from the sale of such power, or from funds, secured by the sale of bonds hereafter provided for, to construct, lease, purchase, or authorize the construction of transmission lines within transmission distance from the place where generated, and to interconnect with other systems. The Board is also authorized to lease to any person, persons, or corporation the use of any transmission line owned by the Government and operated by the Board, but no such lease shall be made that in any way interferes with the use of such transmission line by the Board: Provided, That if any State, county, municipality, or other public or cooperative organization of citizens or farmers, not organized or doing business for profit, but primarily for the purpose of supplying electricity to its own citizens or members, or any two or more of such municipalities or organizations, shall construct or agree to construct and maintain a properly designed and built transmission line to the Government reservation upon which is located a Government generating plant, or to a main transmission line owned by the Government or leased by the Board and under the control of the Board, the Board is authorized and directed to contract with such State, county, municipality, or other organization, or two or more of them, for the sale of electricity for a term not exceeding thirty years; and in any such case the Board shall give to such State, county, municipality, or other organization ample time to fully comply with any local law now in existence or hereafter enacted providing for the necessary legal authority for such State, county, municipality, or other organization to contract with the Board for such power: Provided further