In the demo of the game there is a mission that you have to rappel down a building (FIB) and that you can see the inside of the building.
Is this also for other buildings? Maybe you can get in every building (big ones)
IGN said "airport security" so this means an interior of the airport building.
I think all the big buildings have an interior so you can get in those buildings.
I don't think that there will be interiors for small houses. But I hope te cab interior is better looking then IV's