If our newly consolidated and thoroughly screwed up countywide 911 system could effectively locate addresses on anything other than POTS calls, the wife and I would have dumped that landline in a heartbeat. There have been so many publicized screw-ups with the system over the past couple years, with more than a few people losing their life waiting for help, that my wife got nervous about dropping it when I brought the subject up. AT&T would prefer that everyone drop POTS, since the government won't let them out of their requirements to maintain the system as long as people still use it and depend on it. It's much cheaper for them to switch everyone to VOIP, and that's why they try so hard to convince folks to do so.
Jerry