If that was the case it would probably be a SPECI, either way you cannot use the QNH from it, legally anyway.
In that case, I would use the AREA QNH and add 50' to the forecast minima (unless you had a ground agent that could relay the phone AWIS by radio, or a blue tooth headset and telstra coverage)
I often hear Qlink going into Coffs on the overnight flight asking center for the latest METAR as the tower closes pretty early there. Im assuming this would be to ascertain wind direction and get an appreciation of the ceiling?