And, these taxes have absolutely no bearing on whether Qantas should or shouldn't get a new fleet.
The ICAO ETS is only on International services. CORSIA requires as of CY2019 airlines report pollution metrics. Member states can set their own ETS for domestic operations. This has been done in Europe. Taxation of output could be the next step, this is what is being signalled. This has airline management concerned.
"Excess emissions" charged at the customer interface combined with the growing spectre of flight shaming, as alluded to by Little Napoleon, are the concern. Fleet choices (particularly as it relates to type and configuration) might see a per passenger emissions charge highlight exactly which airlines have "game changed" and those who are busy creating project names or social discourse.