If someone wanted to generate multiple cities to place them all on a larger map, they would want to adjust the coordinates to match their larger map. The larger map is going to have it's own coordinate system. Normally i think it would use Latitude and Longitude. The map I have uses pixels x,y of the most zoomed out image.
If was going to do it, I would write a script to import the city JSON and adjust things, someone else may just want to concatinate all the cities in one JSON file and use it like that.