About the time that I upgraded to 2020.1 I had a project with about 7 street scenarios go haywire. Maybe it was just coincidence (with a mistake I might have made) but it took my a while to figure out that I had to assign scenario membership to the node. This feature is actually pretty useful for street scenarios, but I don't remember seeing any documentation on it until now(?). Perhaps I missed this before, or maybe I made an error that caused me to find it just now... Just thought I would share, Thanks.
Did you use upgraded rules in the mean time? If the parameters change that causes issues. I heard more changes to scenarios would benefit streets, but it does not surprise me the street shapes need consistent scenario assignment.
Do you have the CGA code used to generate those ADA ramps? Are they sloped? Do they work with only a specific corner curvature threshold?
Well, I never really figured out the proper use of scenario management for nodes, because if two nodes overlapped from different scenarios it still treated them in the same space. So the automatic street shape generation would try to create two separate curved roads that didn't overlap between the points (a lemon shape). I wonder if that's a bug or my improper use and/or understanding of scenario management for nodes. However, I could imagine a very good case use of scenario management of nodes if they could exist in the same space without effecting each other. It could serve for better memory management when dealing with large scenarios being able to treat some streets and nodes as shared instances. And changes to one scenario could selectively change other scenarios. The best workflow though imo, is to copy the entire street network for each scenario until scenario management for nodes is more understood.
The ADA ramps, the one you see is a single shape I created in Blender that just gets squeezed into the ramp shapes. The overhead lights are generated from the intersection shape's vertices and then offset beyond the shape's scope. Then I did something to control the rotation and scope. Both of them only work with a specific corner curvature as you suggest.
I have a second ADA ramp code that uses a 2D shape insert and then builds off that using split techniques, roof slopes, etc., which works pretty well, but is also limited to curvatures. But I can texture that one in CityEngine, where the one you see I cannot.