I guess the question is where do SQ's loyalties lie, and (perhaps more importantly) how do the other alliance members perceive it.

What is UA getting out of SQ? Certainly there will be some feed into their domestic network out of SFO, LAX and to a lesser extent JFK/EWR. But they are probably not getting much new traffic out of LHR, where SQ pax are more likely to be fed to VS.

LH and AC are doing better out of the deal, particularly with codeshares between Europe and Asia.

I think SQ are more valuable out than in, if only for their utility as a marketing element. But if UA and LH set an agenda, I don't think there is going to be a very warm reception for any tendency on SQ's part to buck it.