I don't know the answer GW intended, but I have some input on the RAW:

1) Use the highest leadership in the squad for tests.
-It's not really leadership, so not covered by this rule.

2) It is NOT conferred (as said before) according to the BRB, so a fearless IC is no longer fearless when he joins a squad which is normal.

*Scratches head* I'm not sure what happens if they fall back, though... don't fearless models auto-rally?