I don't know if this is a bug or it's on purpose, but we can't select a path with a train that doesn't belong to the route we are on. For example I can't select a destination with a TGV on the new austrian route and vice versa with OBB 4024 on LGV Route.
Is this a bug or this was done on purpose ?
It seems that free roam mode gives us the freedom to do what we want, but not too much either. It's a shame :/