Dick:
Is there any evidence that an ADSB return has been used in this way ?
Given that CASA has a habit of prosecuting pilots from 'desk research" for example the case of John Quadrio and a YouTube video and, allegedly, drawing conclusions from Flight Aware data, it is hard to see why CASA would NOT avail themselves of ADSB data in a prosecution. In fact a good QC could easily make a case that CASA was delinquent in its pursuit of public safety if it did not surviel all data and prosecute detected infringements.
Given as you know, how easy it is to parse a stream of data with a computer,, it is childs play to filter the data for a set of conditions, for example commencing a turn at less than 500 ft and half kilometer from takeoff, low flying, etc., etc.
ADSB will be used exactly like an automotive speed camera. Being cynical, the prescription of high accuracy TSO'd GPS to drive ADSB for VFR is about evidentiary reliability from a judicial point of view for the purposes of prosecution.