"(though I can't help feeling that they didn't expect in a million years to get past the switchboard"

You wouldn't expect to get past the switchboard which is mabye the point. I heard the call the other day and you can hear the guy sniggering in disbelief saying something like "they're not actually putting us through". They knew very well that there was no way they should be put through but didn't care as long as they got their laugh!! No-one could have expected this to happen but they must have known (if they have at least half a brain) that at the very least the aftermath would put the nurses under pressure and perhaps even put their jobs, or someone else's, at risk. Prank calls as entertainment is all very well but the point is there has to be a line. When you start messing with people's jobs you've crossed it.