I had City Engine 2015.0 installed on a computer with standalone license. I then installed City Engine 2015.2 expecting it to install overtop City Engine 2015.0 and replace the short-cut. Unfortunately, this is not what occurred as I have the ability to open both City Engine 2015.0 and City Engine 2015.2.
Is this the expected behavior that both versions would be available after installing the latest and greatest version of the software?
Are there issues that can arise with 2 versions of the software installed on the same machine?
This is expected and should not cause any issues.
Official Documentation: Existing CityEngine users—Esri CityEngine | ArcGIS for Desktop