Baggage make up and sort centre is one of the hottest places on the planet due to all the machinery. It does get an AC supply, but only to cool the components down a bit. It will still be warm. Once your baggage is placed in its bin and heads out to the ramp it will be the temperature of the ramp. The hold will stay warm until airborne, but if live cargo is in the same hold as your bag's bin, then heating is supplied to that hold. In short good luck, I'm doubtful whatever you are carrying will stay frozen for long.