I can confirm that they do indeed insist on ripping out your copper pair. When the power goes out, the battery back-up kicks in: it's rated to run for eight hours, by running for seven and then saving the last hour of juice until you push a "give me my last hour now" button. But the battery won't power your ringer, so unless you happen to pick up at the lucky moment, you can't get incoming calls.

This was what kept us from switching over earlier than we did. I finally gave in only now that we have cell phones as an alternate pathway.