This is nearly always a myth.
On call has a huge precedent, it's not tech, it's the health sector.
"Paid" on call is already defined as the active portion where you're responding to a page, not the passive portion where you're carrying the pager.
Some countries have rules around time to respond within the definition of active vs passive, but most do not and the carrying the pager isn't compensated at all.
Even with the active part, time-in-lieu can be the definition of paid... still 40h per week (or whatever), but if you only responded to 1h of active on call in a week, finish work an hour earlier one day the next week.
People in tech like to imagine that their salary rises by some significant %, but it seldom does... nurses and A&E staff aren't paid far more for being on-call and carrying a pager, and that precedent travels far, countries aren't legislating in a way that makes their health services untenable.
Some countries do legislate hard in this area, i.e. France, but then... they have a much smaller tech sector as a lot of companies will avoid hiring there or setting up an office there (especially when neighbouring countries do not have such legislation).
To be clear I don't know what the exact text of the Australian law is, but I'm just clarifying that on call does not have to be paid, and as soon as one thinks about the health service and the impact of such legislation it's clear why. Sure one can also view this as wage theft in every industry, but in that case workers need to go make that case. Most large companies will likely continue to avoid such legislation by treating their workforce as fluid, and just withdrawing from some countries and only hiring in others.
Note: None of the above is reflective of where I currently work, but are things I've learned from prior places of employment.