Many programs have different criteria for eligible accrual depending upon which version of the program you are a member of (generally based on where you live, or at least have your mail sent to). These are usually based purely on competitive considerations (sometimes on government regulations). Both BA and AA wish to ensure their FFers use that carrier for their major travel across the Atlantic, afterall, they are still competitors for revenue on these routes. Thus you cannot earn miles flying the other.
Since North American FF programs are highly competitive, they generally give credit on all paid fares on their partners. (Some exceptions do exclude the lowest fares, but still include other discounted ones.) Because Asian and European carriers operate in a less competitive environment (each being based in a home country with little or no home-based competition) they can be more restrictive in eligible fares for accrual, or elite status qualification. BA and CX have fare more restrictions on eligible fares for home-country/region based FF program members than other oneworld carriers.
It really is no different from a myriad of restrictions on commerce that exist in countries like Japan and Germany, for example, in the retail sector. That's life and we just have to accept these rules, and learn to live with them. Or change to a program that is more liberal, or get a U.S. or Canadian mailing address (though you may not be able to start award travels outside the region you are registering from!).
Just noticed some of this is discussed in the July international edition of Inside Flyer. Check out the main story on that site.
[This message has been edited by Shareholder (edited 07-03-2000).]