I can't imagine LA would be *that* concerned by MX joining in oneworld - after all, there's not a whole lot of overlap in their routes (and LA and MX codeshare their flights between SCL and MEX anyway).

AA might be more concerned, but again, they very swiftly established codeshares with MX pretty much immediately after they left Star Alliance.

I guess we'll see soon enough - another partner's not a bad thing to have at this point anyway! ^