I would think ACCC are fully aware. I e-mailed last year and I am sure others have. Mine was just a general suggestion that Australian passengers need protection in the same way that European passengers are protected. If Qantas was obliged to provide expensive compensation, I am sure they would suddenly become a lot more careful about how often they did it.
In my opinion Qantas is really working its planes hard, so if something goes wrong with one, these sorts of things happen. I think we can be tolerant of occasional downgrades due to equipment problems, but it seems to happen too often for a whole range of reasons. It is also the way it is handled - often quite poorly. It isn't just business to Y either. Mr FM and I were downgraded from F to J (these were paid fares) and I had to fight to get back into F on another route.
As far as getting a full refund goes, I suppose if your fare conditions allowed you to you could, but often there are penalties. The so called refund that Qantas says it will give you is pathetic. A friend of mine had paid for Premium economy to the USA. on her return leg they were overbooked and at checkin she was asked if she would accept a downgrade to Y. They offered her some sweetners (entry to the J lounge) and a refund and she thought that sounded Ok. On return she found the "refund" between premium and Y amounted to $200. She was totally outraged.