A few niggling points on the whole idea,
1. Shenzhen Airport - the de-facto low cost hub to HKG, flights from SZX to mainland chinese cities are well below those from HKG and local people take full advantage of this as well as incoming chinese tourism (transfers from Shenzhen to Hong Kong are big business with 2 mtr stations, many coach services, car transfers about to be opened up and several border crossing points). As an example at easter I'm travelling SZX-HAK which saved 50% over HKG-HAK.
2. HKG Runway Capacity - A 3rd runway has recently been approved for construction and there are efforts clear up the congested airspace by consolidating other airports in the region. Prime runway slots have already been jumped on by the legacy carriers.
3. CX - As has been mentioned the relationship is poor between QF and CX - they have strong loyalty in their home market and extensive penetration with Asia Miles. They also have a head start on the whole '2 brand' approach with Dragonair already operating on a lower cost base to leisure destinations whilst running an award winning service. CX also already has a mainland Chinese sponsor in Air China backing them who is unlikely to rest on their laurels whilst the CZ/JQ tie up affects their market share.
4. Hainan Group - the so called 'new kid on the block' Hong Kong Airlines has been fighting for several years now bitterly for market share and credibility, it's fares heavily undercut the major carriers to leisure and business destinations already but it is viewed with suspicion locally and is regular fodder for the tabloids with tales of customer service 'nightmares'. Backed by the Grand China group it also has deep pockets to sustain a low fares assault.
5. Other LCCs - 10 other LCCs operate from HKG to Asian destinations already.
I'll be curious to see who is the target market for this new JQ franchise as it is a very crowded market place here already. I'm sure the domestic helpers travelling between Indonesia, Phillipines, Thailand etc will be glad to see further competition on their routes!
Otherwise there is still along way to go for this announcement to be fleshed out into a story for success.