In many Hospitals the use of Mobile phones etc is prohibited in specific areas and around specific equipment. It is usually clearly marked.
The use of 3G dongles and Mobiles in wards in our local hospital has been allowed for some time. (within reason)
In theory specific areas like operating rooms should be shielded anyhow (which isn't hard to do) theres no good reason really to ban mobile useage ad hoc (phones shouldn't really be a problem usually but police, ambulance, etc. short wave can potentially be when in close proximity).