Battle Stations are on the tech tree, tucked away in the hulls research line (odd place, I think). Researching them doesn't give the module....
Battle Stations II, III, and IV appear on the Thalan tech tree, but none of these modules can be installed without Battle Stations I. That module is typically unlocked by researching Space Weapons, but since that technology does not exist on the Thalan tree, they can never acquire it on their own.
I've posted about this issue in Brad's Please Slam My Game
post, encouraging him to add Battle Stations Mk 1 to one of the appropriate Thalan techs like 4D Phasing or Defense Industries. If you agree that's a good idea, please add your thoughts to that thread, too.