All grants of franchises or rights for the conduct or distribution of electric energy, electric power, or electric light within any city or town of the state of Washington by the city council or other legislative body or legislative authority thereof, whether granted by ordinance, resolution, or other form of grant, contract, permission or license, shall be subject to popular referendum under the general laws of this state heretofore or hereafter enacted, or as may be provided by the charter provisions, heretofore or hereafter adopted, of any such city or town: PROVIDED, That no petition for referendum may be filed after six months from the date of ordinance, resolution, or other form of grant, contract, permission, or license granting such franchise.