Max, if your originate line already has the sofia dialstring then there's really no reason to send the call through the dialplan - it already knows where to go. If you want to force the call through the dialplan then use loopback. However, you need some sort of endpoint for that to work. In your example you have this originate line:

originate {origination_caller_id_number=120003}sofia/internal/242424@192.168.50.67 &socket(192.168.50.67:10000 full)

Is 242424@192.168.50.67 a locally registered user? If so you could just do this:
originate {origination_caller_id_number=120003} loopback/242424 &socket(192.168.50.67:10000 full)
 
This would run the A leg through the dialplan to look for destination number "242424" and then handle appropriately.

If I understand your scenario I believe you are trying to get one leg of the call established and then the other leg handled by the event socket. What is the endpoint you want handled? A SIP phone that is registered locally? Or something else? In any case, you can CAN loop it through the dialplan but you aren't forced to do so. Assuming 1000 is locally registered:

originate {origination_caller_id_number=120003} sofia/internal/1000%192.168.50.67 &socket(192.168.50.67:10000 full)

originate {origination_caller_id_number=120003} user/1000 &socket(192.168.50.67:10000 full)

originate {origination_caller_id_number=120003} loopback/1000 &socket(192.168.50.67:10000 full)

NOTE: the first two do not use the dialplan but the third example does. This means you MUST handle destination_number="1000" in your dialplan (which the default config does).

Hope this helps.
-MC