[ruytlm]

My understanding is that the new law still requires a warrant, but that the warrant can be granted by an administrative tribunal rather than a judge - so technically what Fastmail are saying here about only acting on a warrant would be correct.

As per the response from Fastmail, it does still require targeting; the intent of the law appears to be to 'take over' an account and use it to catch conspirators, e.g. "we caught Timmy red-handed planning a terror attack, let's log in as him and tell his co-conspirators to come meet us somewhere, then arrest them all".

Whether or not that's what it will be used for is another question, and a valid concern.