Much of what I said for BoP cutscenes would still apply. I see no reason why you would not have the same choices of what to try to do (full motion, partial motion, or slideshow). However since TG managed to get away from ships-only animations and include some character animation (plus a slight improvement, though not up to the standards of the Rebellion cutscenes) then our own efforts would look even more amateurish.
And unfortunately it also appears that the XWA Cutscenes are compressed with a LucasArts proprietary format, rather than as with BoP being Smacker which was freely available. Unless a converter (AVI->snm probably) can be made we are rather stuck.
Using their cbm (picture) and snm (animation) files though I was able to successfully add a duplicate cutscene onto the end and have it play from the Hard Drive (which had been a problem as XWA plays cutscenes from the CD normally).
The list files you will need to edit and the cbm files for the
little pictures (for the cutscene replay screen) live in the
/frontres/cutscene directory. You will need to add your cbm file
to this directory which can be generated with the little trick Psychic discovered.
Then you should edit Cutscene.lst to add the information that tells XWA what cutscene and what picture are linked. Simply copy and paste a line and substitute your cutscene and picture names for theirs. Note though that although the pictures are *.cbm that in the list file they are *.bmp.
The other line to edit in this directory is Cutscene.txt which is slightly more complex as there are 5 lines of information per cutscene. There is a helpful template at the top of the file though which explains what each line means but I will reiterate it.
First line is the name of the snm file (you don't need to include the extension).
Second line is the name of the cbm file which is associated with the cutscene (the one you just added)
Third line is a description which will be displayed as a label on the cutscene replay screen. Note that the text between the !s is not displayed.
Fourth line is the mission number the cutscene is played on.
Fifth line states whether the cutscene is played before or after the debriefing (in BoP they were played before or after the mission). Most of the TG cutscenes are "0" for before debriefing.
Now we have to fool XWA into playing the cutscene from the
Hard Drive. Fortunately I noticed that the directory structure on
the CD is the same as in the XWA directory which gave me an idea.
What we have to do is to put our cutscene (again assuming we can make them) into the xwa/movies/ directory and then copy disk2.id from the second CDs root directory to /xwa/. This seems to make the game look in /xwa/movies directory as well as the CD movies directory, and fortunately doesn't affect the playing of cutscenes from CD1.