The Employment relations (Triangular Employment) Amendment Act is a more complex piece of legislation which will no doubt be tested by case law, but fundamentally it allows for a third party to be named in a personal grievance.
Whilst who will be considered third parties will need to be established by case law broadly you can think contract milker employees hired to work on a business owners farm as potential groups of employees who may fall into this category. Read more about the Act and what it means here: