Is it possible to specify dial-peer voip to unregistered its E.164-ID onto the GK ?
Wit pots there is no register e164 command but nothing with voip dial-peer.
The no-reg keyword used with the number command on the ephone-dn should do it.
Also try executing a show telephony-service dial-peer command. You should notice that that dial-peers created based on your phones registering with CME are actually POTS dial peers.