I am not familar with the Sup I for the Cat 4 but I would think if it did not support QOS it would still foward this. I suggest you put a sniffer on the other side of the Cat 4 and see what it shows on the TOS byte.
T120 Datashare is a option that is loaded on Windows 2000k server. After you have this installed you have to setup the GW and the MCU to point to the T120 Servers IP.
Are you still having problems getting this to work? Cisco has a fix in the latest IOS that allows the newer versions of H323 in through the firewall. Before this was implemented you had to turn Fixup protocol 1720 off.