China Southern can be very price competitive, a recent search for SIN-LAX return had them as the cheapest by a large amount. Obviously they've looked at CX in HKG and decided to have a piece of the pie.
With Chinese mainland costs being well below Hong Kongs, the Guangzhou region having a per capita income close to western levels and a modern airport not subject to the congestion and delays of Beijing/Shanghai, they could be in with a chance.
FEDEX are already using CAN as their Asian hub, Hong Kong and Shenzhen are next door.
Obviously the have plans for the A380s, China's answer to Emirates/Singapore Airlines if they can improve the customer service a bit ?