Philbky
You are right AKL is not slot constrained, but it just so happens that BNE MEL and SYD are.
There's about a 9hr window for arrivals and departures in and out of DXB that connect Europe with OZ.
So rather than have the aircraft sitting around on contested ramps attracting absorbatant parking fees they fly them 3hrs to AKL clean them and fly them back to OZ dumping seats on the market and code shares with QF.
This way the passengers leave Europe arrive in OZ at the right time and vs versa.
Cheers Enos
Whilst what you say regarding what happens to the aircraft in Auckland is true, the rest is far too simplistic a relating of the story. The Auckland Airport Authority was looking for new services to connect to Europe, only ANZ offering a once a day through plane service over LAX. Other routes involved changing in Australia, Singapore or Hong Kong often with extended layovers.
As you say, Emirates had three aircraft doing nothing in Australia for long periods and, seemingly they were happy with this. The Auckland Airport Authority approached Emirates and offered slots and reasonable charges. They had to make a sound case for each route which took some time and negotiation. The benefit for the airport was not only the easy connection to Europe over Dubai but the uplift on the Australia- New Zealand sector which helped reduce the numbers of 737/A320 flights between the two countries by up to 600 flights a year, important in a country with strong environmental credentials. How do I know this? Because my cousin was Chair of the Authority at the time and initiated and saw through the negotiations.
The New Zealand - Europe market is now so strong for Emirates that an additional service has been started direct to and from Dubai, currently the world's longest non stop service. The story of that service is here.
Emirates Launches Milestone Dubai-Auckland Non-Stop Route