With the student going 1st solo in April, it does seem like this flight is a 1st training area solo. Well done to the student in making a difficult decision.
I would imagine CASA's focus will be on the instructor, in particular the competencies regarding the students orientation in the training area and how to get back to home field. CASA just love looking for the tiniest things, error or contradiction in a training record.
I have done over 400 training area solo checks to date, I make absolutely certain that my student can re-orientate themselves from anywhere in the training area and get themselves home. This is as important as the airwork component.
The Jindabyne Aero club seems to be a pretty switched on outfit, one of the members has written probably the best mountain flying guide I have come across.
Will be interesting to see the outcome of the investigation.
http://www.jindabyneaeroclub.org.au/mountain-flying.pdf