I would suggest you use the "Free" mode of RailClone (you can find it in the Style rollup).
With this mode, RailClone uses the shape of the spline, but ignores its position. Using it, you can move freely the RC object or the spline.
In this way:
1) For each one of the RC objects, turn on Style->Geometry->Free object.
2) You will notice RC is moved out of its original position. That's normal because now the object is built at its pivot position, not at the spline.
3) Realign the RC object with the spline. For example using the Align tool (Alt+A) Pivot->Pivot.
4) Create the house group, EXCLUDING the RC splines.
5) Clone the house using the Instance option.
6) Now if you modify the RC spline, all RC objects will be updated but not moved from their position in the groups.
I hope that helps.