Traditionally, it was unacceptable for landline service, since it's safety critical. (You need to be able to call 911.) I poked around to try to figure out wh

Traditionally, it was unacceptable for landline service, since it's safety critical. (You need to be able to call 911.) I poked around to try to figure out what the current requirements are, and it looks like they've mostly been scrapped. "Central office backup power" is required, which matches my experience attempting to get terrestrial internet or cell service during power outages.