Guess what happened. Right. Nothing.
While asking Microsoft how these new features are working is like trying to communicate with a wall, a nice guy named Etan Bukiet finally helped me a lot. In this thread on MSDN Forums he reports about a conversation he had with the common controls developers. The outcome is frustrating, but at least it brings light in the dark.
Most of these new features are private to Windows Explorer and can't be used by 3rd party apps. Windows Explorer uses some private interface to enable these features of Vista Common Controls. Of course Microsoft didn't consider it necessary to document these limitations. In Redmond even simple information like "this feature is for internal use only" seems to be to secret. Well, I just wasted ~9 months, no problem.

So what does this mean for ExplorerListView? It won't have these features:
- Groups in virtual mode
- Group footers
- Group subsets
- Group extended icons (LVGROUP::iExtendedImage)
- Extended tile view
- probably more