The change in v1.3 was for bridged calls, not just forked calls:
- Allow Caller-id spoofing for calls bridged via OBiTALK service.
Consequently, CallerID is passed on forwarded calls via the OBiTALK service.
Keep in mind that each OBi is limited to 4 simultaneous bridges.
It will also be necessary to disable Call Waiting on the PHONE Port and OBiTALK service MaxSessions will have to be increased past 2 (at least in OBi #2).
Now, having clarified some of the OBi's features and limitations, I think this whole idea hasn't been thought through:
If four OBi's each have different PSTN telephone numbers from Google Voice, the first (main) number can only handle a maximum of 2 sessions. After two calls to the main number, callers to that number will get a busy. The only way the other three Google Voice numbers will be used is if someone explicitly calls them. Only the first two OBi's will get used for calls from the main number.
If you use a VoIP provider on the first OBi that supports four sessions on the DID associated with it, then the second, third, and fourth caller can be passed off to subsequent OBi's as each OBi's PHONE Port becomes busy. In this case, you ony have one main number and no additional numbers to deal with. All calls come into the first OBi only.
It's also an easy task to route outgoing calls from the other three OBi's through the first OBi that has the VoIP provider configured on it.