Open Rails software is designed to be compatible with all MSTS routes. Use the standard MSTS route building tools and techniques to build routes for Open Rails. An Open Rails Route Editor is a ways into the future.
Open Rails software uses the same shape files and texture files as MSTS. All your familiar MSTS model building tools, i.e. 3DC, TSM, 3DMAX, and GMAX will all work. Create WAG, ENG, S and SD files as you have always done.
We don't think we can build full compatibility with existing MSTS AI and Signaling behavior - we think we can get close. And we already added functionality to make AI more flexible and exciting, like enabling AI trains to couple to and drop off cars on their own. On the signaling side, we've started early prototyping of an Open Rails signal system could be including a signal monitor.
As for an Open Rails Activity Editor, well, that's a long, long way in the future.
Compatibility with our software is governed by the content producer. The simulator is currently in the very early stages of development. Today, there are few features available to content developers specific to Open Rails - except the ability to accept significantly higher model poly counts without the need to divide the model into sub objects.
When we reach stage where new capabilities for rolling stock or scenery objects dictates separate Open Rails content, we will release 'Open Rails Compatible' logos to identify content is only compatible with Open Rails.
Open Rails has many limitations and incomplete features with respect to MSTS compatibility. See the Roadmap for more details. We do plan future enhancements beyond MSTS - specifically great water visuals, advanced model shaders, and procedural terrain, etc. We'll implement these in a way that doesn't break backward compatibility.