Looking in the Steam store, the Sims DLC packs have a little banner similar to this:
Requires the base game The Sims™ 3 on Steam in order to play.
My girlfriend has Sims 3 and Sims Medieval through Origin, and was hoping to get the DLC through Steam to take advantage of their sales. Is there any way to get the Steam DLC to work with the Origin base games? I would assume the files are mostly the same and some combination of file copies, editing, and registry changes would work, but I'd like to find out for sure.
Edit: I'm still interested in the answer even if I'd need the Steam base game in order to buy the DLC. I'm also interested in the reverse -- can DLC from Origin be used with the Steam base game?