I've posted AA flights to Asiamiles.
Just tell the agent it's for Cathay Pacific. Mentioning the Asiamiles term seems to confuse them.
AA posts to CX every 10 days or so, so you'll have to wait a bit.
One thing to note is that CX posts real flight miles and do not round up to min of 500 miles. I.e. my DFW-AUS only posts like 150 miles or so instead of 500 miles on AAdvantage.