It's possible that sending in your El Al boarding pass to AA would result in mileage credit.
YMMV.
as long as the tkt# isnt on the BP, havent flown on a paid LY flight so I cant comment on their BPs but most of my BPs have my tkt # on them and 1 look and Bingo if the 1st 3 #s doesnt correspond to showing its an LY tkt. (its sort of like a CC where each set of #s tells them them what kind of CC it is, which Bank or comp issued it etc etc) the 1st 3 #s of a tkt corresponds to each Carrier eg 0161111111111 tells the Travel World that its a UA tkt even if Im not on a UA metal flight, so send in a BP with a tkt# that starts with 016 to AA for LY credit should raise some eyebrows and cause them to look into it
after all I can be on a UA flight IAD-FRA and then be connecting onto an LY flight with ElAl flight # and be requesting credit for the FRA-TLV flight assuming it can earn AA credit, but Id expect once AA sees the '016' that they will want to do a proper search to make sure I wasnt on a UA code-share flight (doesnt exist) before actually giving me any credit. Could be the Right person on the right day wont want to bother and deal with all the checking
nothing to lose but dont get credit on ElAl or Swiss if you are gonna try sending it into AA as theers a good chance they may find out you already got credit for it on whomever
