Interestingly, UA is the only airline that does not grant the 50% EQM bonus on partners, where AA & SkyTeam definitely do. I can't speak for US, and as others are indicating, it sounds like there is a special deal between UA & US on this point. But note that this is not in writing on UA's website for mileage earning on US: link.

I don't have any experience specifically on US, so I can't speak to that point (and the first hand reports here are good news!). But I can speak to this point with other partners, and you definitely don't get the UA EQM fare class bonus on other *A partners . Just something to bear in mind. Were you to do any inter-Europe travelling on LH on full fares for example, none of this would be earning the 50% EQM bonus.