There are long discussion threads here on the AA forum:
http://www.flyertalk.com/forum/showthread.php?t=1107595
..and on the BA forum here:
http://www.flyertalk.com/forum/showthread.php?t=1105334
Obviously lots to be sorted out, but I summarize two main sentiments:
- AA Elites excited to earn/use miles (and hopefully SWUs) on BA TATL premium products.
- BA Elites concerned about hordes unwashed AA Elites consuming space on the same.
My suspicion is that there will be some preservation of elevated access to BA Elites on BA TATL flights. For example there was a suggestion that "upgrades" for AA SWU would leverage WT+ as the "interim step" to CW; so that SWUs would be limited to AA passengers willing to pay for WT+ first.
Stick with BA until it's all sorted out. There's lots of speculation and few facts at the moment.