asterisk users - Aug 2004 - Inband announcement of parking slot from app_parkandannounce?

I'm trying to use Asterisk app_parkandannouce to build a global parking
pool from within a couple of Norstar PBXes. Right now I can blind transfer
calls into the parking lot, but the slot announcement relies on calling back
the 'transferee' after the call is parked and I can't pass enough
callerid
data out from within the PBX to be able to route the call back in (ie. no
PRI facility, just cT1). 

 With the Norstar a two-step transfer (Feature-70) can be performed where
the caller is placed on hold while the 'trasferee' converses with the
'transfer target' and eventually 'joins' the caller and the
target. This
would permit the 'transferee' to hear the slot announcement before
joining
the caller to the asterisk system.

 So, the question becomes: How do I structure my extensions.conf to convince
app_parkandannounce to play it's message on the incoming channel rather than
using dialback? Have I simply missed a switch somewhere, or will I have to
use some sort of meetme bridge configuration to short-circut the incoming
call with the announcement? I sense that this might be related at least in
part to the occasional requests to the list for app_park to pass back the
results in a ${PARKEDSLOT} varable.

Any suggestions considered...

Kris Boutilier
Information Systems Coordinator
Sunshine Coast Regional District