Thanks for the question. In this scenario the house will be instanced as a single object, at present RailClone treats a nested style as though it were a single static mesh. Of course this mesh in then instanced so unless it contains tens of millions of polygons you shouldn't have a problem.
The only exceptions are if a segment is sliced or deformed in which case just that part of the mesh is rendered as static geometry, or if you use the segment's Nest
option to force the randomisation a nested style's parameters. In that case instancing is disabled completely.
I hope that helps, please let me know if you have any further questions.