We have emergency warning systems that can do all the modern stuff like cell/tower area broadcast/push, websites, data feeds, and radio/tv station protocols for major enough events… which are all nationally coordinated, but actually activating them is delegated to state level control, so a national emergency is passed down to the state emergency management organisations… but while Australia would absolutely know we’ve got nukes incoming (5 Eyes intel, and our own massive over the horizon radar systems) and probably have some idea where they are headed… that’s a military matter with no publicly documented process.
We have a publicly documented process to handle a biological incident (weapon or accident doesn’t change how you deal with this much once it’s happened) and we’ve got a publicly document procedure for re-entering space debris (which we’ve actually used recently due to some random spaceX debris in a farmer’s paddock) …
But we have no plan for if we’re going to get nuked… which is only partly understandable.
We’re not exactly spread out enough that a dedicated nuclear attack couldn’t exterminate >90% of the entire population of Australia. Depending on the missile and it’s MIRV/Decoy ratio and the yield of the weapons, you could probably get above 90% with 3 or 4 ICBMs. There’s no infrastructure for sheltering, and we’re completely unprepared for the aftermath, having a plan that details how fucked the survivors might be is … not something I think a lot of government ministers want to sign their names to… bad optics…
However the counter argument is we’re a major US ally providing material support to US overseas military power projection by way of naval ports (which we just made more important as part of our sub deal making those ports more useful for US nuclear submarines) our significant regional radar coverage (JORN is quite the beast of a radar) and us hosting secure downlinks for the US orbital assets covering this hemisphere and us hosting a major communications facility which would likely play a role in ensuring the final communication of orders to submerged nuclear ballistic missile submarines in the event that a nuclear war actually happens. I find it hard to imagine Australia won’t have at least a couple of nukes headed out way somewhere early on the list of targets even if it’s not so much about Australia as it is about destroying and degrading the ability of the US armed forces to operate in the indo-pacific region.
So on the one hand… probably going to happen in the event the shit hits the fan so hard nuclear war starts… on the other hand there’s not a lot we can do to prepare or defend right now against the sudden outbreak of nuclear war. So why worry anyone with detailed plans for horrific doom. Sure if tensions rise we might get some US missile defence systems that could help make it less doomsday, but that kind of military planning is probably a classified bullet point on some future planning list based on one or more of the treaties Australia has with America already.
Oh and there’s the classic “On the Beach” if anyone is looking for more of this kind of horrible disaster scenario stuff.