Looking at the xml, It's unclear- how do I connect city level-up to the city's special improvement? I see that CityHub1 turns to CityHub2, but in no place it writes for it to pull the 3 special buildings, and to transform to one of the specializing city types.
Also, is it possible to "pull" the city's level for production? Or, to auto-upgrade a building with city-levelup?