I did a first aid course for work last week, the lecturer was a former fireman, I mentioned this having seen the vid on a f/b page. He said it's an urban myth (ie bollocks), emergency calls work everywhere, if you've got no signal the phone will say emergency calls only. 112 is used in many countries as the emergency number including UK, but we originally had 999 due to it being the shortest number to dial on old style phones.
