Perhaps what I hate most about the BA/EI relationship is that BAEC members crowd our Priority lanes, get access to our lounges and even try for Business class checkin. That's fine as long as it is reciprocated! One time a BA Gold cardholder asked me whether I should be in the Priority queue (on an EI flight!), from thereon, I enforce the fact that I get priority boarding, lounge access and fast track when using BA that have EI codeshares, I usually get away with it.