EI has recently entered into interline agreement/codeshare with UA; possible, if not probable, that there's a co-ordinated move here: BD out (well, to LHR) and EI in.
EI is talking about setting up a cabin crew base in the US (which has been greeted with less than complete enthusiasm by EI staff), so maybe this is involved as well; the new CC bases will be SFO and two others, which I can't recall (JFK and ORD, I think); if these are correct, two - ORD and SFO - are UAL hubs.
EI has two new A330s coming next year (although it is losing two older ones) ...