That doesnt help when a natural disaster cuts power to an area for more than 24 hours. Cell towers dont have multi day battery capacity and with everyone calling their loved ones in the effected area they will be even more congested than normal. So even if they do have power your still likely to lose signal when the towers get ddosed by everyone trying to use them at the exact same time.

You see the same thing happen when theres a mass shooting and you get tons of people calling 911 and then you get a ton of people calling their loved ones to find out if theyre okay.

The cell towers also rely on an internet backbone so if you lose power long enough to lose internet then you lose cell towers even if they have all the power they need.

You could try putting all the communications infrastructure on a high priority circuit or something but unless your going to build out a hardened power grid parallel to the existing one, that would only cover you from load shedding not from natural disasters or even just power lines sagging on a hot day until they short circuit and blow the grid. So im not sure it would be worth the cost.