Link to Devstream taking a first look at the private beta TSW Editor built on top of the UE4 Editor is
here. This mostly covers scenario creation including using assets from other DLC in the current one although there is a brief overview of route creation facilities at the beginning. It certainly shows there will be a bit of a steep learning curve for those unfamiliar with UE4 but it also gives glimpses of additional facilities available such as AI coupling and uncoupling and AI interaction with signals.