Really there is little benefit using proxies in RailClone.
Probably you noticed they consumes less memory just because object is not generated completely. All sliced and bended segments (which requires more resources) are not being generated.
Proxies should be used only for complete objects (cars, trees, etc.). But even in this case there is not a noticeable improvement, because RailClone already generates instances both for meshes or proxies, when possible.