Southern Cross set up a team of specialists ten years ago because they believed that ACC was wrongly turning down legitimate claims by policyholders, leaving the Southern Cross to pay the cost of treating them. 'The insurer said it scrutinised around 200 cases a month where policyholders had had claims declined, usually older people whose injuries ACC concluded were wholly or substantially caused not by their accidents, but by underlying medical conditions. Usually age-related degenerative conditions.' Click here to read more from Rob Stock. The emphasis was added by me, that is a very large number of claims - something like 24,000 claims since the team was set up by Southern Cross.
You should read the whole article. There is a wealth of claims data on the number of claims that were subject to some sort of dispute, the number of decisions changed, and the amount of money that is at stake. $4.95 million in payments made by ACC to Southern Cross in the year to June 2016. More than that, is the extent of the process Southern Cross engages in.