SPC the workers were unanimously in favor of the mandate, so no court action would get legs seeing the company consulted the workforce first and is acting on best available medical advice from external sources. BHP was dismissed on a technicality that they had lack of consultation and that the requirement was not included in workers contracts, the latter was the main sticking point that the commissioners said if altered would change the outcome. So like with SPC if the workforce is united in wanting the mandate the contracts can be altered and the mandate valid.
Both of those workplaces are closed shops, not really public facing, so not comparable to airlines where you are transporting the general public. With any company that is mingling with general public you are going to have different angles much more agreeable to mandates, particularly if the older or vulnerable are involved commonly.
Where anti-vaxxers would be really screwed is if the workforce agrees generally to accept vaccination as a contract/EBA condition. Then there is no recourse as that's the agreement.