They can say what they like, and I am a customer, but in hand-wavey generalization terms one should be aware that Australian law enforcement has excessively broad access to telecommunications data on request and a long history of doing the bidding of the United States. Carriers are forced to retain your data for 2 years.

Under TIA Act provisions (such as s180), an authorised officer of a criminal law‑enforcement agency can authorise access to prospective telecommunications data [metadata only; not whole messages] if satisfied it is reasonably necessary for investigating an offence punishable by at least three years’ imprisonment. (In other words, ~any time they want)

Example: the data‑retention regime’s records were being accessed over 350,000 times a year by at least 87 different agencies, including non‑traditional bodies such as local councils and the RSPCA [pet cruelty nonprofit].

Given Australia's population is only 28M, that means roughly 1 in every 80 people gets communications metadata pulled by their own government annually.

Yep, I am a fastmail user, born and live in Oz. I just assumed that this data would be collected either on this side or via the US servers. Also, we are still a part of the 5 eyes alliance.

The only way to win the game is to not play.