There was a royal commission years ago into the criminal activities of another union- the Costigan Royal Commission into ship painters and dockers.
A lot of stuff was found out. The union no longer exists- but there's no way that the one union had exclusivity.
In fact the royal commission found activities that extended into the top end of town- it uncovered what became known as the "bottom of the harbour" tax avoidance schemes, which were costing hundreds of millions in foregone tax.
The commission became a de facto investigation into organised crime. It famously named Kerry Packer as involved in a corrupt transaction, something which was never proved in a court of law.
When it finished it morphed into the National Crime Authority, which later merged with other authorities to become the Australian Crime Commission.