Emergency status
I found it interesting that (based on my interpretation of the LiveATC.net recording) the crew had to taxi to the ramp to get the engine inspected after landing (where the emergency vehicles were apparently waiting), apparently crossing at least one other runway in the process.
There did seem to be a vehicle or two following the aircraft however I would have thought it best to land , taxi clear, then stop. Then get fireys to have a look and then get them to follow to the terminal.
As for PAN vs. emergency - I think the crew conveyed the message to the ATC (except the bit about dangerous goods) well enough - as some kind of emergency response was waiting when the aircraft touched down.
I agree though I would have thought QF would have announced the PAN earlier. This recording makes it sounds like they are returning for anything but an engine-out scenario.