Oooh, I have Back In Time on my Linux machine. (You do know that modern Macs run Linux under the hood, don`t you?)
Knowing how Back in Time works, and assuming that the relevant parts of Time Machine work similarly, be advised that any back-up program that operates on a file-by-file basis can leave in files that updated assets have deliberately removed. Trainz` own internal back-up system works on an asset-by-asset level, which handles orphaned files correctly.
On the other hand, most of the content is stored in *.tzarc files, which means that you probably got lucky, as those also represent an entire asset.
You are probably ok doing it this way, but be prepared for occasional oddball issues that no-one else can recreate. Of course, any time you mess with the trainzbase with external programs, you`re likely to require a rebuilding of the index.
Edit: If you just delete the entire asset directory before the restore, all of the points that I`ve been trying to make are moot.
