It strikes me that there are possibly two planned reasons for Swiss to move it's FFP to BAEC.

1. The trans-Atlantic issue mentioned earlier. I'm not sure of the T's & C's but as I understand, it's not possible to earn BAEC status points or miles when flying AA and vice versa across the pond. So even if you did fly Swiss from ORD to ZRH for example, you'd only be able to pick up the miles on your BAEC membership. The AA / BA Duopoly is preserved.

2. Financially, this is an additional bonus for Swiss as it essentially unloads a liability from the balance sheet not to mention the cost savings of not having to maintain lounges, TC call centers, etc. BA picks up more 'direct' access to a new and potentially lucrative customer-base through an under-the-radar transaction no one noticed in any of the press briefings I read today.