I solved my original problem (meter not working
http://forum.cockos.com/showthread.php?t=190696) and used some spare time to do some tests.
Result: In my configuration the "VU X" parameter set to any even number let the track meter work. Setting it to an uneven number = No meter on this track.
Has maybe something to do with # of stereo channels or multi metering...
Anyway, my curiosity is satisfied so far...