TLS is unaffected by any government laws. What I assume OP is referencing is a law that makes end to end encryption problematic in Australia but Fastmail has never offered end to end encryption. Neither do most email providers so it doesn't matter.
If you get a PGP browser extension they all do. It’s pretty inconvenient to use though, sending encrypted attachments and giving the password offline is probably the only thing most people are up to.
The location of the fastmail office has zero impacts on this. If the complaint was that the PGP extension was developed in Australia then that would be a valid complaint. But email hosts themselves are not private against government requests.
