That's annoying as I had a lot of last minute reservations on CX in the past (and they have historically loaded a lot of seats at T-48h). I can now see all this availability through Qantas but there is nothing available through BA website. When I call AA, some, but not all of the flights that I see through the QF website, are available (I think this ties into another rule - that AA only sees seats on CX if there are more than 4 seats available - i.e. if 6 seats are showing on BA, AA will see 2).
Having said that, it appears that at least some of CX's availability is there when you call - I just rang BA and what they were telling me roughly corresponded to what I saw on QF's website, and I was able to book a CX flight (LHR-HKG) for tomorrow in J.