I remember sitting on a train just outside Harpenden station in the late 1970s, waiting to hear which excuse would be used out British Rail's list. They came up with a new one though: Somebody had stolen the signaling cables!
As for being sued, the idiot will probably say that the PoCo didn't do enough to make him aware of the dangers of cutting live cables. Such is British "justice" these days, that the fact that the thief shouldn't have been there in the first place doesn't seem to count for much.