Originally Posted by
izzik
It sounds like
CargoHoldFlyer has the right theory. First overwater carrier determines the fare used. QR has higher DONEx fares than BA ex-CAI, so if you choose "...DOH-BOS..." then the QR fare below kicks in. Note that this is separate from the carrier that actually tickets the booking (QF for the majority/all of oneworld.com bookings).

I'm not sure about that theory to be honest because I just changed mine and dropped RJ. The price went down about AU$250 from lower YQ and taxes going QR to DOH directly. I know QF adamantly reprices everything so if that were the case wouldn't they now be using the QR fare instead if the RJ or QF fare? I do recall the QR fare being at least $200 more than the ones priced in EGP.