So I just did some research and Dr. Luke isn't bound to RCA Records specifically. He is bound to Sony Music, which is in charge of about a dozen labels like: Columbia Records, Epic Records, RCA Records, and Roc Nation. The other labels are either country labels or minor imprints that I don't believe release music on their own. Dr. Luke isn't allowed to work with artists from other labels outside of Sony Music (except for Katy Perry).
So Hilary is likely signed to either Columbia, Epic or RCA, which would make sense considering Luke is EXPENSIVE and I couldn't see Hilary spending that much money working independently, especially when Luke is bound to Sony Music. RCA seems the most likely, but we can't be 100% sure yet.
Just a tidbit I thought I'd throw out.

What label would you rather Hilary be signed to?
