Q.Sig Path Replacement

Hi, is there anyone manage to get Q.Sig path replacement work in latest Asterisk? Based on some info i found, I try to set the following in zapata.conf


What I have are 2 * boxes connected to each other (E1 euroisdn). I register 2 sip phones in Box A. I am trying to make a call from one of the sip phones and the call is then routed to Box B via the E1 link, play a voice file to prompt the sip phone to enter an extension number (which is the second sip phone number), once entered, Box B will call back to Box A through the E1 Link. Eventually both sip phones talks to each other and I would like the channels occupied earlier to be released.

In Box B, I have

exten => _9XX,1,Answer ;incoming call from Box A
exten => _9XX,2,Background(demo-thanks) ;Play a prompt
exten => _9XX,3,WaitExten,5

;when 701 is keyed in transfer back to Box A via the E1 link
exten => _7XX,1,Transfer(ZAP/r1/${EXTEN})

However the Transfer command never send a call to Box A but instead the call disconnected (hangup)

I did not find much info regarding path replacement when searching around. Has anybody manage to get it work?