Flyboy - try looking here:
http://www.ird.gov.hk/eng/pdf/e_dipn10.pdf
Page 17 - Ship and Aircraft Personnel.
Generally OZ based guys spend more than 60 days per annum in HKG and the base has not been onshored so I think they still have to pay HK tax - would love to find out if this is not true and therefore the admin. of having to do HK tax as well would vanish.