I don't know what voltage it is, but assuming it is a distribution cable of some sort. If it's LV there is probably not much in the way of ground fault protection other than the fuses. It would have to leak several hundred amps before a fuse blows.
I think it is safe to say that something wasn't done the way it is supposed to, e.g. earthing of the cabinets, or some of those darn copper thieves have been at it. (Those are by the way a real danger. I had to call the train people a few weeks ago to inform them that thieves had stolen all the green and yellow cable from a station. Every metal pole and light was ungrounded!!!
[This message has been edited by C-H (edited 07-31-2006).]