I actually participated in the discussions at the time and you are correct that they did not put anything in the final ruling (and then therefore my hesitation) but did say in meetings that "one allowance means one allowance" repeatedly and mixed carrier in same class was more of a priority to airlines at the time (I was on the automation side). But that the "most international" portion of the ticket drove the allowance - so a within euorpe sector on a ticket between US and EU would look at the first marketing carrier (unless they said look at the international carrier) and the first transatlantic sector (I think). I have long since moved on / retired so my knowledge is stale. And award travel is a whole other can of worms.