I have heard many extol the virtues of thawing pipes this way. I have also heard of the current goint "the other way," and backfeeding into a panel and causing damage.
So, what to do? I cannot discount the hazards that might be created- remember that current takes ALL paths, not just the easiest.
I suppose that, if this was a recurring problem, I might consider oversizing the pipe, and running a length of self-regulating Raychem ice melt cable inside the pipe. This might be a way to free the wires without creating a hazard, or damaging the wire insulation.
