Since a forwarded call is actually a new call with the other call bridged to it, the forwarded calls almost always carry the cid of the new outgoing call.
The ability to send the cid of the original call would be a feature offered by the provider that forwards the call. Since obi is not a provider, but a device that is placing an outgoing call and bridging the original call to it, it does not pass the caller id.
I don't know for sure but perhaps callcentric can provide that service, but only if the call is forwarded there and not at the Obi.