Not exactly the same, but perhaps a useful data point...

I've booked BA F using AAdvantage miles a few times before (and have never been more than AADV PLT), but have secured 1A/1K when desired thanks to BAEC Gold status (even though the redemption was made with AA, not BA).

I know it's worked via YouFirst - I think I've even done it online before. I simply asked BA to place my BAEC number in the booking, specifically mentioning to them that I already knew I wouldn't earn miles, but that I wanted it there for seating choice and potentially better handling in case of IRROPS.