asterisk users - Jan 2006 - Line transfering calls back to asterisk system from another pbx

I have asterisk hooked up to another pbx via a pri span. I want to have 
a call come in via SIP to the asterisk box, then go out to the other 
pbx. The other pbx will then call another number through the pri span, 
and out the asterisk box via SIP. I then want to connect those two calls 
together and have the calls both go off the pri span and be patched 
together on the asterisk box.

If I do this on the pbx connected to telco, its called a release link 
transfer, or a 2 b channel transfer. I also do this through an analog 
T-1 with a flash. Does anyone have know what you need to send asterisk 
to tell it to do this, or if its even possible?

-- 
Michael Sampson
Information Systems Manager
Customer Contact Services
msampson@yourccsteam.com
952-936-4000