The multi category feature (component release 2.2.0beta3) uses the new catmap table. However when importing from a csv file the categories entry is put in the categories column of the #__jevents_vevdetail table and no entries are created in the catmap table. Without those entries the events don't show up in the front end.
As a workaround I created a trigger on the #__jevents_vevent table to create these entries. This worked and confirmed my analysis. I assume you want to fix this bug?