Hi not a legal expert at all but this link has some information...

Hi not a legal expert at all but this link has some information I found useful
https://www.claytonutz.com/knowledge/2015/december/engaging-an-expert-for-dispute-determination

in particular

"Some contracts provide that an expert determination will be final and binding unless a notice is given within a prescribed time-frame ‒ in which case the dispute may proceed to arbitration (if prescribed) or litigation. If the contract is silent, the expert determination will be final and binding, and may only be overturned in limited circumstances discussed below."

The announcement clearly states "final and binding", and if you read through the section in the link above regarding "limited circumstances" it appears it would be difficult to get it overturned unless the expert acted outside their contractual powers or the determination was deemed illegal for some reason.

However enforcing the determination is another matter

"Notwithstanding the limited avenues for challenge, there may be a practical difficulty in enforcing an expert determination. In the absence of a legislative framework or court order, a party could choose to simply ignore an expert determination. In that scenario, the party seeking to enforce the determination would need to approach the courts for an order giving effect to the determination. In such a scenario, the benefits that an expert determination can provide, including the informality, cost-effectiveness and confidentiality, may be lost through no fault of the complying party."

It then comes down to how far MIN want to push things. Having said that, if they did push things it would seem by that stage if PLS were forced to court to get an order to enforce it they would have a strong case based on the precedent quoted in this link

http://www.cbp.com.au/publications/...medium=syndication&utm_campaign=View-Original

"In Shoalhaven City Council V Firedam Civil Engineering Pty Limited [2011] HCA 38, the High Court held that expert determinations will be final and binding unless the expert has acted outside his or her contractual powers or the determination is otherwise tainted by illegality."

Cheers