Ma Bell has her own power supply. Phones work off 48 volts DC suppied by batteries and if power fails they have generators to charge the batteries. Better yet if he wants them too stay off land lines then cell lines would apply as well because cells must also use land lines. Cell towers also have their own back up power.
Power is not the issue, it is infrastructure: phone networks are not designed to be used at high usage rates (not too many people on at the same time), and that is the issue.
As elpinta said, the problem isn’t the power supply (even the generators will only last around 24 hours though), it’s the fact that the system can’t handle that kind of load all at once. If everyone crowds the circuits at once, it WILL crash the entire system and that includes 911 systems as well. I know this because of the 10+ years I’ve worked for Verizon and now Frontier as a Outside Plant Engineer.