Do you really need trunktracking? When the call are setup it stays on that frequency for the whole lenght of the call. Just scan the voice channels.
If you need to filter the calls to only monitor certain TG's then you'll have to use one of the available computer programs that decodes the datachannel, often works from the earphone jack, and then the computer sets a scanner to the voice channels frequency. When the call are cleared the scanner are automaticly set to scan again. When I use that program with a UBC780XLT it uses the scanners display to show TG and UID of the call. If the same scanner are used for control channel as the voice channels then the program mutes the audio while it is on the control channel and needs the control channel audio taken from a source that do not get muted, discriminator tap or line audio. But I haven't seen any program that are able to control a Whistler scanner.
/Ubbe