Thanks Cozy, really appreciate your time to provide this information. That now makes it a little less straight forward however.
The rest of the pipe looks stock as far as I can tell based on searches and images, and it seems that BMW, or whoever installed it, simply cut the rear muffler off and installed a BMWP muffler via a twin bolt clamp.
This seemed like a very strange way to install a factory certified component, however it seems this is how it is done.
The dealer provided me with the rear (cut off) muffler, that is all. As above, do you see any good reason I couldn't simply use the same clamp to replace the existing muffler?
The car is very loud however so you're making me think there is more to this PE than just the rear muffler.