cdda-fs (which lets you mount audio CDs and access tracks directly as WAV files), stores each track’s number as an attribute of its corresponding WAV file. For some reason though, Be does not make this attribute visible by default.
To make track numbers visible in the Tracker, launch the FileTypes preferences panel and navigate to audio/x-wav (not audio/wav or similar — double-click multiple WAV entries in FileTypes to see their internal names if you’re not sure), and click Add to add a new custom attribute:
Attribute name = Track
Internal name = Audio:Track
Attribute type = Integer 32 bit
Visible, not editable, display width 20 (or whatever.)
Close FileTypes, then close and re-open the WAV folder on the CD. You should now be able to show the Track column by enabling it in the Attributes menu.

Adam N (nanovivid@bigfoot.com) notes that this tip also works with the x-cdda filetype, as used by CDPlayer.