I am sorry but my answer is unlikely to be a lot of help. There are very few cash machines at CLK as it is, and I do not think any of them have RMB. There are plenty of ATMs in China in the major cities.
The only likely place to find a machine is the China Ferry section. The airport has a map of all ATMS, link is
http://www.hongkongairport.com/eng/s...money_amer.htm
The only ATM machines I know of in Hong Kong dispensing RMB are Bank of Chinas on the KCR at Sha Tin and Lo Wu. In town there are quite a few fx shops specialising in RMB.
Note there are Travelex there who change money at zero commission, however they do not need to charge any commission considering the utterly outrageous bid/asks. And yes I still forget to change money before going to the airport.....................
For what it is worth the best rates I tend to come across for smaller currency transactions are at Wing Hang Bank. Hongkong Bank rates are @#$%.
Delta Asia used to be the best before being shut down in HK reputedly for laundering money for the Russian Mafia and North Korea!