All of the telephone "remotes" (small slave switches connected via fiber to the master CO downtown--they are in single-story buildings about 20 feet by 20 feet) here are backed up with a diesel generator. They of course also have battery backup.
Several years ago, many smaller ISPs did not have diesel generators or sometimes even adequate UPS capacity. They were too busy spending the money on wall-mount plasma displays, conference room interior decorating, and Aeron office chairs to be concerned about such mundane things.
Now most ISPs outsource their dialup access to companies that specialize in this. They do a much better job of it.
