Online piracy has been common for many years, and this legal action seems an obvious action by the copyright holders. So why hasn't this been tested in an Australian court before now?

My understanding is that statutory damages in Australia can't (don't?) reach the stratospheric "$5000 per song" amounts that legislation in the US allows for, which makes the endeavour less profitable.

I'm not sure what's changed from (say) 3-4 years ago on that front.

$5,000 per song plus a sound public thrashing and ownership of your firstborn. That's the only appropriate penalty per song.

I might feel differently about alleged piracy if they could prove pirates are lost sales. But they lost that argument long ago.