I was just sitting in the new Premier Lounge which is located upstairs, so can confirm 100% that it is open!
They have advised me that its not possible to pay cash for entry, you must be flying Business Class with one of their partner airlines, or hold a relevant airport lounge membership such as Priority Pass.
We were quite surprised to see the numbers of Qantas and Virgin gold and platinum members, as well as those wishing to pay cash, attempting to access the lounge. I would estimate 15-20 people were turned away in the space of 1 hour.
The lounge isn't overly large, which probably explains why they're not offering cash payment access.
The food and drinks on offer are surprisingly quite good. Anker beer, wine, soft drinks etc.