This is a very minor thing I spotted last night. I was at war with Procipinee early on, and captured one of her towns. It was in the process of building an iron mine. Thing is, she had researched the mining tech already whereas I hadn't. But after I'd captured the town the mine carried on building and was built fine. So I had a working iron mine before I had the tech to build them.
Sure if I capture a town with extra goodies I haven't got yet I should be able to keep them, but surely I shouldn't be able to carry on building them?