Give TIVO Tech support a call and ask if they can arrange a conference call between you, them and Comcast second tier (TIVO has a direct number that we don't have).
This is correct. your new TIVO units *must* have some connection back to the mother ship. Either hardwired ethernet to each one, or the WiFi adapter on each one or else a phone line on each one that is capable of supporting a 2400 bps "modem" call. (Skype & MagicJack won't work for this, but Vonage will)You don't have internet in the house?? Do you?