But consider that in the US we use GSM-850 (chan 128-251?) and GSM-1900(chan 512-810?). Since the API *DOES* expose the channel id and you also know the carrier of the device (AT&T in my case), could you not deduce the frequency the BB is using?
Unless my thought process is flawed, I now should be able to assume what frequency I need to repeat in my home:
The channel id is 609. I would guess the BB is locking onto a 1900 MHZ signal...?