From my understanding of the Mainland pilots issue from way back, the company were told by the then CAAC in no uncertain terms that they were not to recruit from China. The mainland carriers were having enough trouble recruiting staff to develop their own airlines, at RMB35,000 a month, without the competition of HK.
The pilots I met in Beijing around the year 2000 spoke excellent English and had the same spectrum of ability and experience as any other country. They would have been an asset to CX.