Here in East Texas when you call 911 from a cell phone, they put a lock on that cell phone so you cannot make any calls out to another number. I don't know about if you were to try and call 911 again if it would work or not. Then after the officer arrives and deals with the cituation the hold is released and the phone goes back to working as normal. This has happened twice to my cell phone.
Once again a stupid .gov solution. Anyone wanting to make a fake call, whether for diversion or malice or whatever, can buy a $30 throw-away cell and drop it after the call. For that matter, ANY cell, activated or not, is required to complete 911 calls, so a person could use a deactivated phone, an old phone, whatever. The only people hurt by "locking" the phone are the rest of us who try to do things right.