Most modern data centres wouldn't have had this issue, at least in in Australia they use Argonite suppression systems, these work by using a gas that is a mixture of argon and nitrogen that suppresses fire by depleting oxygen in the the data hall.
Is the situation "Halon is legal in Australia" or "Halon isn't actually illegal per se if you don't use a lot of it"?
Other gases like argon or FM200 are not Halons.