Is this possible? The usage is like this:
Incoming PSTN line is split from the wall to go to 1) UC520 (FXO Port 0) and 2) home phone.
UC520 should not answer incoming calls on FXO port 0, but should be able make calls using FXO port 0.
You can use CCA to configue inbound call routing so the FXO goes to the extension assigned to the FXS. If you need CLI, you can use "connection plar opx" under the FXO port and point to the number assigned to the FXS. The OPX keyword causes the call to connect when the FXS user answers and not before, therefore reducing the chance for FXO disconnect issues.