There's no way to export the procedural representation in it's 'procedural nature'.
Though we're currently working on the so-called 'Procedural Runtime', which is basically an SDK which you can tie into any 3d app and get back the models directly into that app (without need of CityEngine). Though that's a thing to arrive and is not yet available.
At the moment, I'd try to export your model to either .obj or .dae ( Collada ), and then automate the task of importing the new model again into Revit. That way, you just have the basic 'current model' sitting in a specific location in your project directory, from where it can be overridden from CE and loaded into Revit.
That's the fastest it get at the moment.
So you have to find the export format which currently works the best for you. (Currently, there's no possibility to write custom exporters. But e.g. .obj and .dae are ascii-based formats anyway, if you prefer this.
current export formats of interest for you :
- .kml / .kmz( = georeferenced dae )
- File GDB (Esri format)
Additionally, note that CityEngine does not create 'BIM-Models'. What you are creating is indeed a 'dumb' polygonal model, but next to the geometry, you can of course also export metadata for the geometries and export them also via Python to e.g. a text file, ready to load elsewhere.
Let me know if this helps and if you have more question.