Of course its a bluff. Lets take UK for example. Have a look at the CoSUK, can get it out of crew direct. Not only is the basic salary lower but a HKG based guy is getting TWICE as much when you look at basic salary and housing, well over twice if they are taking the rental ceiling after 8 years. For a junior CN, I know there are not many, if any, on UK base but a HKG based CN taking the rental ceiling again is on over twice a UK based CN. Factor in education for hkg based, up to 20K GBP per year for each child attending a boarding school.
Even if CX had to pay all the tax and hire extra guys to cover all the mandatory holidays they would be better off than having everyone returning to HKG. I believe HKG expat housing will die then maybe bases will close but we have a while left before that happens.