So...so far this is what I know. It is aluminium insert sleeve in carbon frame.
What I donīt know - is the alu-sleeve factory inserted (more less permanently) or not? And why no snap-rings?
That alu-sleeve has something what I would call build-in stop for BB30 bearings not to go deeper in frame. A really couldnīt identify it as a snap-ring and I could not remove it.

I hope my Rotor 30mm to 24mm BB converter will fit in it. Seems like it will...