I have found that in colder weather I can never guarantee that the bladder hose or mouth piece will not freeze up even when insultated. Some things that will help are to add a bit of salt or gator aid to the water which will help lower the freezing point and you can also blow the water back into the bladder so that it does not freeze in the tube.

If I am doing an overnight trip I always use a wide mouthed bottle in a cozzy and store it upside down so that the ice forms in the bottom first.