Fastmail users should be on notice with this legislation if they chose this service for privacy/security purposes.
Indeed. Fastmail is no longer secure by law as it is now illegal to have a secure service the moment a govt official asks for access.
https://fastmail.blog/2018/09/10/access-and-assistance-bill/
Which drives home the point a lot of people are forgetting: it was never secure to begin with, unless you were going to the effort of encrypting all your own emails client-side before sending, and only communicating with others who did the same. Fastmail was never an end-to-end encrypted service, so they already could have been served orders from a government to hand over data, and if that government had jurisdiction and the orders were properly formed for that jurisdiction, they would've had to comply.
So as bad as this bill is, it doesn't really change things for Fastmail.