As a rule, all the inflator devices I have seen freeze when you try to activate them. As long as you do not touch them, they do not inflate. If you get pinned underneath the ice, all modern BCs - have a venting valve in their backside. You can vent in any direction. So an inflated BC is not that big an issue when you get down to it. Besides, you should never use it, unless you need it. If you need it, then you have another problem altogether.
A.P. Valves in Britain makes a variety of BCs, some of which have a high pressure bottle, as an independent inflation source. There is no low pressure mechanism on some of these systems at all. You inflate the BC with a high pressure valve, and the chance of a freeze up is very unlikely. So there are alternatives and you should ever say lightly "this is something that you have to do." It is also something that we need to work out the procedures for, better than we have done so far.