The AA website at http://www.aa.com/i18n/AAdvantage/ea...hayPacific.jsp is quite clear on this issue

Earn miles when flying on Cathay Pacific marketed and operated flights for travel on an eligible published fare ticket. Miles are also earned on Cathay Pacific codeshare flights operated by oneworld carriers and oneworld affiliates.

It needs to be a CX flight or a codeshare on a OW carrier to be eligable for mileage accrual to Aadvantage

Each airline's page on Aadvantage details what flights are eligable for that airline and for that airlines's codeshare flights