"the type of person that would go round photographing patients is not the type of person to be hampered by being asked to turn their phone off"
Yes. We have ways and means of dealing with anti-social folk like this. Trust me on this.
I do not know what it is like where you have been but mobile phones to be honest are more of a disturbance to the peace and quiet than anything else but the photography issue is of course also an area of concern.
From my point of view, basically it's like this.
If you're reasonable about your phone use and have been reasonably courteous and civil, I would usually turn a blind eye unless you're really close to certain areas, for the aforementioned reasons.
Usually these folk actually ask for permission to use their phone, and usually they get a yes from me dependent on the situation. If I need to move them, I usually tell them where they can go and stand and all is well.
If you're some nasty rude prick, however, you will be asked to turn it off.
I usually do not ask a second time.
Moral of the story: You come into a hospital, you don't disrespect the place or the people there.
Oh, and by the way, I think most doctors are usually more pissed off than you are, about having to carry pagers. This is beside the point, but old style pagers as you know, only receive, they do not transmit. There are new VOIP devices however, that are necessarily wifi devices, of course.