Hug - would have been a problem with the old networks, but not with the new networks....
Having said that (places engineer's head on) I'm talking 'in theory' - I would like to see it tried in practice, although preferably when I don't have an important call to make!!
I'm not totally sure of my facts here, even though I'm working for a mobile company right now (switching engineer), but I do know a man who will be able to enlighten me.....
Will post facts/apologies/told you so's after checking with him.....