It appears that you want the ability for someone to place a call on behalf of someone else, and transfer to him/her while ringing remotely.
If so, I think the procedure is first call or be called by "someone else", then initiate a blind transfer to the third party.
I agree that even transferring a new call while alerting would be useful for example when an operator is making attempts to reach a busy destination on behalf of someone else, and transfer before answered.
Hope this helps, please rate post if it does!
My case is different;
I want from the opearator to connect me to a outside customers mobile telephone, than hangs down.
Operator calls mobile telephone by using FCT (GSM-TO-GSM). FCT doesn'nt return CONNECTED SIGNAL.
Operator Telephone shows "RING OUT" even in connected case. So Trnsfer button never appears.
I try all signalling options. Nothing changes.