not just Australia, it's world wide and likely led by the FBI (but possibly data being collected outside the US to avoid the need of having actual warrants) The following thread looks at some of the opened court documents today: https://twitter.com/ericgarland/status/1402100449013125123 (and points out that the Trump organisation might be in trouble ....)
But, I don't see how he the tweeter could be sure or know that Trumps used this app?