Originally Posted by London Dude

Correct. When I had no status a while ago I did it many times upon arrival at MAD on a long-haul IB flight in J and connecting to a short-haul IB flight in Y, and I'm pretty sure that the same rule applies if arriving on any oneworld flight and connecting to another oneworld flight. You'll need to show both the business class BP from the CX flight and the Y BP for the upcoming IB flight at the lounge entrance.

I was on separate tickets BTW