There were some packs of all of the missions from the older games to XvT for coop. I was wondering what the most recent versions of these mission packs are (and where I can download them)?

I remember the versions I had were a bit buggy.

A bit more research - these were early parts of the Tie Redux and X-Wing Redux projections (Eventually ported to XWA).

However, I believe the XvT versions may never have had English briefings (only the Spanish version was ported).

More research (and actually finding extant copies) is required!

It shouldn't be that hard to port the missions of X-Wing and TIE Fighter over to XvT. IIRC XvTED by Troy Dangerfield can open their mission files and save them as XvT-Missions.
Furthermore, all we need is this ship pack and all ships from TIE Fighter are in place to port the missions over:
http://xvtedicion.es/ingles/descargas/paqopts/c_paqopt_ing.php?id=4

I'm not sure how to handle the Deathstar missions though.

Here is a Technoplex blog entry about porting the missions to XvT, I bookmarked this bit earlier:
http://imxn.net/wordpress/?p=566
I quote: "The worst thing is that this too is a project that I can’t release!"

He also mentions that a similar project which converts TIE Fighter's mission for XWA was shut down.
As far as I know, that project, called TIE Fighter Total Conversion, is still in progress.

The projects were never shut down, all of them were finished.

wwwDOTmaxgamesDOTit/xwc

Replace DOT with .

Note that the projects at http://www.maxgames.it/xwc/ are all conversion to X-Wing Alliance, instead of XvT.

And you can get the TIE Fighter Total Conversion from here:
http://www.darksaber.xwaupgrade.com/

That one is outdated and incomplete, it's only missions 1-7 and it doesn't even work with GOG version.
The one from maxgames is newer, has all 13 missions and works with GOG.