If you place a wall, it will cast a shadow; a wall with a cut-out has a proper shadow for its out line when lit by sun or moon. Create an open topped box and the interior is in shadow; so far so good. If you add a roof to the box and then replace a the wall facing the sun with a cut-out piece, place a column in front, the shadow is cast properly through the cut-out and into the interior.
The problem only arises when a camera is moved inside a sealed building. Then it automatically lights up when it should be dark. This would appear to be a design decision related to the camera, as it is contrary to the physics modelling that is happening with the walls themselves. It makes some sense when you are building to have that light available, but it makes no sense on the ride cam. Even when building, in order to see your lighting effects properly you should be able to see the interior with it's proper lighting conditions.
Obviously, I don't know why they've done it like this, but it seems that all it really needs is the camera to work normally inside a building and for a 'flashlight' toggle to be added so that you can see the interior fully lit for object placement or in real lighting conditions for checking the look and for the ride cam when you are passing through a building.
EDIT: Where things get really weird is the behaviour of in-game lights. Unlike sun and moon they do not lead to shadows. This leads to bizarre effects like the one below: