As far as I know cell towers all have backup power. After the initial overload of calls passes (texts will not normally have this problem) you should be good for at least several hours if not a few days before the cell towers run out of backup juice.
WARNING & DISCLAIMER:
SELECT AND USE OUTDOORS AND SURVIVAL EQUIPMENT, SUPPLIES AND TECHNIQUES AT YOUR OWN RISK. Information posted
on this forum is not reviewed for accuracy and may not be reliable, use at your own risk. Please
review the full WARNING & DISCLAIMER about information on this
site.