> It appears from some limited testing that the original caller id is always
> shown when the call is transfered.  Is there some way to have the person
> making the transfer show up as the caller id?

To answer my own question it appears that the information is available
in the sip_h_Referred-By variable.  E.g.:

 <extension name="system25_park">
    <condition field="destination_number" expression="^\*5$" />
    <condition field="${sip_h_Referred-By}" expression="^<sip:([0-9]{4})@.*$">

allows the station id making the transfer to be known when a call is
transfered to *5.  The station id can then be used to park the call in
the proper fifo.