I don't have access to any GDS, but I've seen a few data dumps over the years where the same RTW fare was quoted with different prices starting in the same city depending on the carrier. I suspect it's a desynchronization issue with the various systems the airlines use. It appears the AA fare and the BA fare are different, due to a loading error on one of the two systems. I remember some ex-CAI fares for the *A RTWs being different; AC was quoting the old prices, whereas LH and SQ had the new, much higher ones.

Much like with "tax harmonization" in the EU, you can wager your donkey that the least favorable option will prevail. I know of no instances where the carrier-based price differentials have been arbitraged successfully.

I fear we're going to be synchronized to the higher EUR fare in eastern Europe.