Depends on how you look at it. It is a different connections system in many ways, so could be considered so. My opinion is that it isn't - because it's not really a building system at all. The parts are made for each set independently and aren't intended to fit into existing or other sets. My bet is that the add-on walls for this set wont fit into any future sets any better than the last castle parts fit with this one. Compatibility with existing systems is something we need to keep pushing Playmobil on until they comply better. We did our best at the meetings in Germany to get this across but I'm not feeling particularly encouraged about it yet.
