That feature could be very useful. But if (in midi piano roll, in audio, I didn’t try) the track loop length is more than 3 bar, 4 bar, for instance, the track loop starts in its middle while the project tracks start at the first bar !
So the track loop is not synchronize to the project if it’s longer than 3 bars ! Really a pity because it’s much easier to work on a track loop where one sees the playback cursor than making editing in a shared copy container when the cursor is not in it.
So the track loop feature is not usable for a longer than 3 bar loop. Maybe I’m wrong but please, tell me how to use it correctly, then. 
The track loop feature which appeared in cubase 5.0 (if I am not mistaken) never worked correctly when longer than 3 bars. Maybe, it’s time to fix it ! 
299€ the update I paid from cubase 5.0, I’d like to have old issues like that fixed !
Thanks for your attention…