FrankD,
Can you reach the echo test? : **9 222 222 222
If so, then the most likely reasons for a busy would be:
1. You're dialing the wrong OBiTALK number.
2. The OBi whose OBiTALK number you're dialing is not connected to the Internet.
You say you can reach the remote OBi via **1 (Google Voice). Do you mean the remote OBi has a Google Voice account configured on it and you're calling the remote OBi's Google Voice number? If so, that would seem to indicate it's connected to the Internet.
If you can configure the remote OBi, temporarily add an Auto Attendant rule to the beginning of its SP1 (Goolge Voice) InboundCallRoute to:
Voice Services -> SP1 Service -> InboundCallRoute : {aa},...
Then call the remote OBi's Google Voice number. When you reach the remote OBi's Auto Attendant, try calling **9 222 222 222. If this works, try calling your local OBi's OBiTALK number from the remote OBi's Auto Attendant.