Platinum Studios does not own Top Cow. Top Cow is their own independent production company. Platinum only owns (has a contract) a portion of the titles, film only, such as Magdalena, Aphrodite IX, Vice, Witchblade, Necromancer and Hellbound, to name a few. The newer titles they do not own. Top Cow has alot of other titles that are under different movie companies or simply in comic form.
At this time, I do not think Artifacts is located under Platinum, but that does not mean something could be negotiated.
IMO
BTW, looks like Platinum has added some new stuff to their webpage.