Hi tias,
This is because SAIL/asterisk isn't listening to the calling side of the call.
Usually in business, the sequence is that inbound calls arrive and are distributed using DTMF. Outbound calls usually don't need to signal anything other than a dial, so we don't listen. However this might be usefull in the case of call park/pick-up and transfer so I've logged it as an enhancement request.
We can have a look at a hack for you but it may take a day or two - we are very busy just at the moment.
Kind Regards
Selintra