Hi,
Yeah. You set the rule files, you set the start rules and then generate the models.
So as long as you have the Start Rule defined within the assigned Rule File, you can create the resulting geometry.
So e.g. you can create Streets with a Street Rule File and Sidewalks with a Sidewalk Rule File or completely different define all Start Rules within one big myCity.cga Rule File which is assigned to all Shapes, such as e.g. in the Paris Example.
Note that I always code with colors in CGA, which shows me what I'm doing. I'd say you should do the same.
Note too that I created the curved streets with the Edit Street Tool. Hit the 'c' key when you have a street graph selected, then edit the street in the viewport. Add more subdivisions to make it smoother with the precision attribute in the Inspector.
m.