No, it's not possible to get a INode in all cases. TRCInstanceV400::node works only for non-geometric objects (lights and so).
There are two reasons for this limitation:
a) Geometry can be embedded in the RailClone object, without any reference to INodes. This happens for example when you delete the source node from scene. In this case, RC keeps a copy of the geometry internally.
b) Some segments generate a different mesh from the source node. Geometry can be deformed, sliced, etc.
As you can see, this work very different from Forest, where all items are instances of the source INodes.
Another option would be to convert RC to standalone objects, using RailClone Tools. It creates the required INodes for each segment, keeping the instances where possible.
Can i ask what what game engine do you use ? We're evaluating to provide exporting tools for Unity, Unreal, etc. in next versions.