The authority and power granted by RCW 35.92.280 through 35.92.310 is an additional grant of power to cities, towns, and public utility districts to acquire and operate electric public utilities, and the provisions hereof shall be construed liberally to effectuate the authority herein conferred, and no restriction or limitation prescribed in any other law shall prohibit the cities, towns and public utility districts of this state from exercising the authority herein conferred: PROVIDED, That nothing in RCW 35.92.280 through 35.92.310 shall authorize any public utility district or city cooperating under the provisions of RCW 35.92.280 through 35.92.310 to condemn any property owned or operated by any privately owned utility.