Regardless of the temporary prohibition or restriction of use of streets under the powers conferred by article 11 (temporary prohibition or restriction of use of streets), a utility undertaker is at liberty at all times to take all necessary access across any such street and to execute and do all such works and things in, upon or under any such street as may be reasonably necessary or desirable to enable it to maintain any apparatus which at the time of the prohibition or restriction was in that street.