[cisco-voip] Call Preservation using SIP?

[Robert Kulagowski]

2851 running 12.4(11)T1.

Our remote sites are configured for H.323 to support call preservation 
if the site goes into SRST mode.  However, with H.323 we lose inbound 
caller name.

I've setup a lab and have configured SIP trunking; using a SIP trunk I 
now get caller name delivery, but seem to have lost call preservation.

Is this a misconfiguration on my part, or just not possible with SIP?