What happens if an animal walks through the laser beam? Do the police drop everything and come over every time? If she needed the police for a genuine reason and they couldn't show up because they were checking a breach in a laser beam somewhere else then she'd be the first to complain that they weren't doing their job.
She would be expecting this pair to turn up all guns blazing, Mabel would be armed with a double barrel shotgun while riding Peggy as her security steed.