4. Regardless of the temporary stopping up or diversion of any highway under the powers conferred by article 13 (temporary closure, alteration, diversion or restriction of streets and public rights of way), a utility undertaker is at liberty at all times to take all necessary access across any such stopped up highway and to execute and do all such works and things in, upon or under any such highway as may be reasonably necessary or desirable to enable it to maintain any apparatus which at the time of the stopping up or diversion was in that highway.