Actually, the engine is different from most of other procedural engines in that it uses satellite height data for the terrain, further refined down to centimeter details. It's a real world location shown in the above video.
It does not use satellite imagery though, because that's not automatically refineable - can't easily add detail to it, unlike with the height info. However, it can use other data (essentially land class style info) to seed the procedural generation in a way that will enable you to match the look of the terrain without the effect of civilization. Atop of that you then use vector data defining how the civilization changes the nature (roads, fields&pastures, later also urban areas). So, while it doesn't let you use the imagery directly, and you'd have to vectorize it first, once you do so it will bring you a consistent level of detail down to the ground level.
Also, the engine tries to do everything graphics-related on the GPU, leaving CPU for simulation and game code.
