Re: Multiple redundancy
The mobile network shouldn't get locked up. the GSM specification means that emergency calls are specifically flagged in the communications between the mobile and the base station, and if the base station is busy, it must drop an active call to allow it to service the emergency call.
So in theory, emergency calls from mobiles will always be able to be made.
Also, around the turn of the millennium, because I was working for a radio station deemed critical infrastructure, my mobile was put on the system as a high priority device - after all, if it all went wrong on NYE 2000, they needed to get hold of me to go into the station. Oddly enough, for several years until my number was removed from that list, I never had any problems phoning friends/relatives or texting around midnight every new years eve!