Hi Taoman:
Sorry; I don't understand your post.
The original poster was asking about this scenario: They have enabled Google Voice's call screening feature, which allows the GV user to press 1 to accept an inbound call, or press 2 to send it to GV VM.
If GV is forwarding to, and thus ringing a Google Chat client (or, an OBi pretending to be one), GV implements its call screening feature differently, and so GV isn't interacting with the OBi to control call screening.
If GV forwards the call to a forwarding phone number, such as a mobile or landline number, including SIP VoIP ITSPs like Callcentric, then yes, the feature does work, and the user can enter the 1 or 2 to control the handling of the call.
It's possible that some ITSPs may be incompatible with GV, if they are also doing something with early media on their own system (not GV's system), but I have been using GV call screening with Callcentric for several years, and it works perfectly. The key here is that GV needs to detect that the called party has answered the phone call, not whether GV is, itself, using early media.
If that is not what you were asking, please try again.