Scientists in Germany have demonstrated a startling new form of surveillance: identifying people using nothing more than ordinary WiFi signals. By analyzing how radio waves bounce around a room, researchers can effectively “see” and recognize individuals — even if they are not carrying a device and even if their phone is turned off.
FWIW I was able to use my own router when I set up with Xfinity recently
This was fiber, if that makes a difference. I asked the install guy, he called his boss, because no one had asked him that before. He told me “no, it’s not allowed”. Also, I tried plugging the patch cable directly into my own wifi router and nothing.
The router would need to be explicitly configured to connect to your account on the network, which would require certain information provided by the ISP, which it sounds like they weren’t going to provide.
All inferred from the response I got from the tech.