All phone calls go through a switch. This has not changed since my working in telephony in the 80s and 90s. Take out the switches and it’s over. They has enough enough backup power for 3 days.
Regardless of the local switching center using copper end-to-end or fiber-to-the-block, the heavy aggregate traffic of phone and data are now routed out of urban areas over optical fiber. Trunk fiber connects these large population centers—loss of the trunk connection largely isolates such a region from the outside world.