This depends on what exactly you are playing, doesn't it?
ASC got more than one ruleset.
Also, it obviously doesn't contain copyrighted BI data as such, since it's FLOSS, but can import on the fly BI data (art and scenario) you have and enable BI rules (more relaxed resources-wise). The compatible unit set you may need is mk4 (it got "Demon" infantry unit and so on).
The maps also can be converted with two clicks in map editor using .ascmapxlat files (which is a bunch of resource ID substitution lists in plain text) into default resources with Mk1 unit set (native ASC campaign), Mk3 (the one trying to be slightly more "realistic") or your own custom resources (which you may neatly pack in a single whatever.ascdat file if you want to).