I got all this info from several different AA reps. I'm not sure if it's 100% accurate and that's why I wanted to post. I could see the ElAL reps saying "we don't care what AA told you" for sure.
However, I am talking about connecting flights and not stopovers (meaning 1 ticket). Most carriers- brussels, Finair, AA (at least OneWorld carriers I checked) from Europe only allow 1 bag now. I think Iberia was the last to allow two free bags. So with the rules I layed out, if you are using ElAl to go to connect in any destination in Europe and then are taking AA across the water- AA's policy would go. That makes a big difference, because ElAl's policy on a second bag to Europe is 1.5% of a Y class ticket per kilo which is like $15 per kilo or $300 for a 20kg bag, while AA is only $50 for a second bag. Unless you are saying that since ElAl would be tagging them to NYC they would apply their 2 free bag policy? That's a great question.
Anyone else have any experience with that situation?