2. Don't forget that cost is one of the factors. I believe that when using partner lounges at outposts, CX pays the lounge operator a fixed price per CX guest. So that is one of the factors, too. Frequency probably has something to do with it, as well. CX has four LH flights/day at LHR, so not terribly surprising that they have their own lounge. Likewise at BKK, for example, there are currently five flights/day, and I believe that there have been more in the past. At JFK, OTOH, three flights/day, but they use the BA lounge. LAX has 2-3/day, shared OW lounge. SFO, two/day and I think that they use the BA lounge.

4. I'm not sure that I understand your question. Are you saying that OW carriers should never fly on the same route? I don't think that that's the point of the alliance, and there are numerous examples, -- AA/BA TATL, BA and CX LHR/HKG, to name just two. Could you be a little more specific about your question?