I may not be accurate, but I would assume it would work the same way as Skype, through the internet to internet path, or internet to landline. On skype there is a charge to go to a landline, but I would assume the charge would be encompassed in the monthly service charges for phone etc. here.
Well, here's how I thought concept Go V Phone might work on IPTV.
First, IPTV remains as an additional box (like an Apple ITV box) in a theatre set up.
A very good Cam somewhere capturing the "Watcher(s)/User(s)" in High Def (low and regular lighting) +
A Vonage "like" Telephone line (s) _ all IP naturally,+
On screen "EASY TO NAV" Video phone capabilties +
Friends and Family Offer (every major LD is drooling for an upsell)+
Multi window "CONFERENCE" abilty (Chat room style a la X_BOX)+
Intelligent Browser abilties (BING+OPERA+CHROME ON STEROIDS) +
Program the new 65 HDTV for multi window and run the XBOX, CABLE, IPTV and PHONE CON-FRANCE all at once "SHARING, BLENDING, PLAYING SOCIETY NETWORKING IN A CLOUD WITH YOUR NETWORK"...
+
PROGRAMS BANNED IN EVERY COUNTRY OF THE WORLD+ THE MOST IRREVERENT CONTENT "EVER" + (Adolf Hitler in Drag is a good start)