All ordinances granting franchises, or extensions or renewals thereof, shall reserve to the city the right to terminate the same and to purchase all the property of the utility in the streets and highways in the city and elsewhere, used in or useful for the operation of the utility, at a price either fixed by the ordinance or to be fixed in the manner provided by the ordinance granting the same. Nothing in such ordinance shall prevent the city from acquiring the property of any such utility by condemnation proceedings or in any other lawful mode, but all such methods of acquisition shall be alternative to the power to purchase reserved in the ordinance granting such franchise, extension or renewal as hereinbefore provided. Upon the acquisition by the city of the property of any utility by purchase, condemnation or otherwise, all franchises, extensions and renewals shall at once terminate.