Manoverde84 - Generally the firms that design those buildings will have an in-house interior design department. Usually the people in those departments have an Interior Design degree.
My two cents on the whole discussion:
I have a BS in Interior Design, and did a lot of research on programs before choosing the Art Institute. If you want to get an Interior Design degree, but work at an architecture firm, I think what matters most is choosing a program that is VERY technical. I worked at an architecture firm while I was in school as a draftsperson, because my program was so CAD heavy, I was able to jump in with architects and keep up.
My mother is an architect, and originally encouraged me to go for an Architecture degree, but now she is happy that I went with Interior Design. We have a firm together, and typically look to hire designers with an ID degree rather than an M.Arch. In our experience, designers who have only gone through an architecture program tend to be more conceptual thinkers, which is harder to apply to real-life.
I'm generalizing a bit of course.
I call myself an interior designer, but I get called a decorator all the time. If you don't have an ego about it, who cares? I know I'm not a decorator, my clients know what I am capable of, that is all that matters.