sbiddle:
They have obviously had to dig underground to get the CATV coax into the building so it seems really strange that they didn't run multipair copper at the same time as this is fairly typical. It sounds more like a stupid decision made by the developers at the time!
It could be possible that they ran pairs into the building but have used them all.
Anyrate, its cheaper to get a VoIP line. And the moral of the story is forget iTalk, go with 2talk or WxC.