Have had it done at my folk's house several times by the municipal water dept when I was little. There was a curb box meter that they used for one connection and the other went to the incoming pipe in the basement. It can present a distinct fire problem depending on where the leads are connected and how the electrical system grounding and bonding is performed. The current doesn't care what pipe is frozen...just looking for a return path or paths! Somewhere I have an article about a fire caused by this process. If anyone want's to email me a FAX number I'll try to dig it out.
