Cecil,
I wonder if it was a utility company of some sorts? Since your mother said they were pushing wires in the ground, they could have been using a probe rod to find a water line. I have to locate our waterlines everyday and that involves me pushing either a 4' or a 6' probe rod into the ground to actually touch the main. Like us they may not have a lot of tracer wire installed with their older mains. If they were in the right of way or a utility easement thats all they have been looking for.
