I'll just note that in the last few weeks there have been reports of a security guard in a NZ quarantine hotel getting Covid-19, and two security guards at NSW quarantine hotels getting Covid-19. One of the security guards in NSW who tested positive was also fined a couple of times for breaching self-isolation orders.
This is why I've repeatedly questioned whether elimination (rather than aggressive suppression) is even possible. It is not acceptable to keep people out who have a right to be in Australia (I'm already not happy with the limits on number of people returning and with how people on temporary visas have been treated). And no quarantine system, no matter how carefully run, is ever going to be 100% perfect. Maybe our quarantine system in Victoria was worse than others - I haven't been keeping up with the inquiry too closely, though it sounds like some bad stories have been coming out - but I believe most or all of our cases originally trace back to one or two quarantine breaches, and we know of multiple quarantine breaches in other jurisdictions. Maybe we handled those worse, or maybe we just got unlucky.
But to me the more concerning thing is how the contact tracing etc. worked after the breach, because NSW's experience - difficult, but just about keeping on top of numbers - is much more how I expected Victoria's to go.