assuming a standard 001 AA ticket credited into an AA frequent flyer account -- and therefore mileage credit is 5X fare paid (plus elite bonuses) -- the relevant question would be how AA apportions a single thru-fare across multiple segments. would it be via the same basis that AA refunds the value of the unflown segment (B to C), as per the excellent advice of donotblink above?

i don't know the answer as I credit AA domestic to BA and intl to AS.