Wow this stuff is old news.
It's standard engineering procedure on many aircraft to "burn out" oil residue contained in the aircon distribution system when it gets noticably stinky by running the aircon at max temp on the ground for a while.
As for the potential of health effects, I am sure it can come down to genetic pre disposition, however I have never seen anyone directly effected by this.
The amount of oil vapour that escapes in to the cabin is nothing like the amount that ground workers are exposed to at every shutdown and startup. Refuellers are almost constantly getting it in the face on A320's, and aside from it's rather unplesant odour and lingering oiliness on your clothes, I can't say I have observed anybody becoming ill from it.
The article describes "chronic health problems, including fatigue, sleep difficulties, fluctuating gastrointestinal problems, numbness and tingling in fingers and toes, memory loss and word-finding difficulties".
Many of these can be explained by the nature of airport work - shift work causes fatigue, sleep problems, memory and cognitive impairment. Tingling fingers & gastronomic issues each have many other causes as well.
Surely New Zulund doesn't need to launch an independent enquiry in to something that has been done to death throughout the rest of the world already !!!!!