Hi Jim,
Assuming you are talking about AUDIO tracks,
you would need to OPEN (not Import the CWB) to have tracks separate, as originally saved.
I believe in order to IMPORT separate individual tracks from one project to another, in the original project, you'd first EXPORT each track separate, onto separate files. Then you could then, in another project, IMPORT them one at a time.
If you import as you say, then a Mix takes place onto one track.
This is my limitted understanding, but maybe there's a way I am not yet aware of.