I am not entirely sure I understand your question, but I am assuming that you are importing a road into CityEngine that has certain height values at each node and that you'd like to set height values for the road in between the nodes to get a finer resolution.
In this case, I would recommend that the workflow would be to set the height values of your road at the desired resolution before importing into CityEngine. The road you import into CityEngine should already be the desired resolution. This would be a cleaner workflow than trying to translate and rotate street shapes to achieve a higher resolution street in CGA. Then, once your street is imported into CityEngine, you could use CGA rules to build on top of the imported graph network.
However, to answer your first question. Yes, you can access the object attributes of a shape from within your CGA file. If you have an object attribute named "height", then you can create an attribute in the CGA file with the same name "height", and the rule attribute will get its value from the object attribute. In the Inspector, you can also link the attributes (if they don't automatically link), by clicking on the arrow next to the value field of the rule attribute and select "Object Attribute" as the source.
