I'm not entirely sure what you mean by spatial relationships, but in your example, I think you want some houses to have gable roofs and some to have shed roofs depending on their position in the world. This you can accomplish by converting scope coordinates to world coordinates with the convert() operation.
convert Function
In general, knowing information about other shapes is currently difficult and limited in CGA. There are the occlusion queries that allow you to detect if something intersects/touches another shape, but currently, that's about it.
Occlusion Query Functions
Python may provide more options for this. For example, it is possible to get a list of shapes in the scene and get their positions.
