How about we clarify a few things here, shall we?
From the AIP: "Emergency Fuel" - when the calculated useable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing can be made is less than the planned fixed fuel reserve".
From the AIP: "Minimum Fuel" - when having committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance will result in landing with less than planned fixed fuel reserve.
So let's look at the case of QF108, for example, that flies from LAX to SYD. They probably leave LAX with an 06-12 TAF for SYD. If that TAF has any probability of fog below alternate criteria, the aircraft will have alternate fuel or, if unable to carry that amount, will be expected to divert at DPA (the waypoint before PNR).
Inflight, approaching DPA, if the TTF (which supersedes a TAF during its validity) has any probability of fog, then the aircraft will divert if it has insufficient fuel to fly an approach at SYD and then divert. If the TTF has no requirement for an alternate, the aircraft will continue to SYD.
Now if after passing DPA (with no alternate requirements forecast on the TTF), SYD unexpectedly fogs in, the aircraft is committed to a landing at SYD. Would the crew plan to fly that approach on their last drop of fuel?? NO!! They would probably hold for as long as they could, and then fly an approach so that they would land with more than FFR! Therefore, no requirement for a MINIMUM FUEL call, or an EMERGENCY FUEL MAYDAY call! Right?
Is a MAYDAY justified (grave and imminent danger to the aircraft and passengers and crew)? I would argue not. Is this a PAN (abnormal operations) situation? Probably. Would Sydney protect the localizer in this situation? I would imagine so, if the pilot declares that his intent is to carry out an autoland.
The Qantas fuel policy is approved by CASA. Any other operator could use a similar policy within Australia if they choose to. Okay?