Loopstart signalling does not pass and digits. The only indication a LS trunk gives that a call is coming in is the 80Volts AC ring signal.
By default, the FXO port will sense the ring signal, go off hook and play dial tone. This is called two stage dialing. Your config is set up to do this.
To make the call work using 'single stage dialing' add the following command under the voice port -
connection plar opx
Where is the extension on the CallManager that you want to map the call across to.
When a call comes in with this config, the voice port senses the ring signal, then automatically makes a call to the configured number. This matches on the voip dial peer and rings on the IP phone. The voice port does not go off hook until the IP phone (or voice mail) answers the call. Since the voice port does not go off hook until the phone is physically answered, the PSTN caller hears a PSTN ringback tone as well.
