I'm not sure which thread I should post this in, but AA, IB, JL, CX, QF and probably all other oneworld carriers except BA now allow (in fact, require) the use of the F bucket, not the A bucket, on the AONEx products on BA flights on LON-DXB and LON-BOS.
e.g.,
Code:
>$LB14/BA
014 LONLON 16DEC18 AA GBP 9595.00 AONE3 STAY---/12MBK-A
FARE CLS EXPLANATION BOOK CODES
-------- ---------------------- ----------
AONE3 FIRST CLASS AROUND THE WORLD FARES A
AONE3 APPLIES FOR ROUND TRIP FARES
AONE3 FOR ADULT
BOOKING CODE EXCEPTIONS FOR CARRIER: BA
VIA BA NO BOOKING CODE DATA EXISTS FLTS
4130-4149
VIA BA NO BOOKING CODE DATA EXISTS FLTS
4550-4579
IF VIA AA A- FARES
VIA BA F REQUIRED BETWEEN LON-DXB
IF VIA AA A- FARES
VIA BA F REQUIRED BETWEEN LON-BOS
The exception actually comes in as a common override for all "A-" fares including travel on BA flights; it isn't specific to the AONEx product.
This also prevents the usual rule for downgrading to D, E, L or Y if those classes are full or unavailable for booking, so the exception may be reworded.
BA has touched their table but not yet in a useful way.