I highly doubt it, but I want to make the greenford branch and I want it connected to GWE. Is this possible?
In TSC doing route extention was much easier cause of how it was built etc. In TSW there isn't a route dependency like x route is needed for y to be visible or to work on.
Scenery and probably track can be added to existing routes (the enhancement mods for example add scenery), but you can't add signals so you probably couldn't have AI use it, you could probably only drive on it in free roam. You also can't change the existing stuff.
So your issue with adding track to a route is the dispatcher will only see the track that was in original and not what you've added due to it being all cooked. Plus there isn't any way to make sure the player requires the base route so your possibly going into areas of redistributing a payware product which isn't allowed.