The reason why they have no community transmission is because they don't have open borders and very strict quarantine procedures. They have to wear masks even outdoors and also have a check in system.
Have you seen their purpose built quarantine camps?
They enforce up to 3 weeks quarantine. If you get caught as a close contact at a facility, you get bussed away to quarantine. There was a person leaving HK that tested positive a week after arriving at their destination country. Everyone that was a close contact the week before he left was taken to quarantine. Imagine the uproar if that happened here.
The NSW Government has relaxed restrictions too fast. Sure, allow most things to open up and operate as normal but QR code check in and masks should have stayed imo. Allowing music festivals shouldnt have happened. Would not be surprised if EPIK last weekend is a superspreader event.