I'm travelling to New Zealand, and my itinerary mentions a technical stop in Australia.
Will I need to apply for an Australian transit visa for this?
Yes you do! I had a flight from Europe which included technical stop in Sydney and I found about it the hard way - I was banned from airplane in Munich on 6th of February because I didn't have transit visa for Australia although I have passed passport and custum control! Chief of staff of Emirates airways airplane didn't let me on the plane because i didn't have a transit visa for Australia! I spent next week exploring about it and after visiting my Ministry of foreign affairs and phoning australian embassy I got a clear answer: transfer visa is required even for a very short technical stop! Unfortunately, I have lost a very good 10 days of holiday (not to mention financial loss) because travel agency didn't warn me about it :(
Normally on a technical stop passengers remain on the aircraft while they take care of whatever the reason is for the stop. Likely in your case, since it has been scheduled in advance, they are stopping to refuel.
As there is no disembarking or embarking, there are no immigration issues or requirements.
I am posting this as an answer because I would like to get downvoted if I am wrong.
The other answers seem to indicate that you dont need a transit visa for landing and taking off from Australia, however if I read this immigration authority page and then proceed to read the exception list in this page from the same site you will need a visa if you are not one of those specifically exempted.
My thoughts are kind of semi-confirmed by this forum thread which says
mandatory transit visa as long as flight lands on the airport.
So you may do yourself good service if you ask your travel agent / visa consultant to check this to avoid being denied entry into the flight.
A transit visa is absolutely needed if ones nationality/passport holder's country is mentioned in the Subclass 771 requirements for holding a transit visa for AUS. There is however a list of many countries not requiring a transit visa for layovers less than 8hrs. But some large countries like China & India require their passport holders to have a transit visa for any kind of layover or travel through AUS i.e even a technical stop.
I learned it the hard way when I was recently stopped from boarding my flight on EK413 which was CHC-SYD-DXB as one flight number and same aircraft with a technical stop, as I wasn't holding a transit visa. I also learned, that pax deboard during this stop with cabin luggage and re enter the same aircraft and assigned seat after going through a security check again in the transit area.
So do NOT be misinformed by the above posters as they are referencing to other kinds of stops in other countries and/or other nationalities that do not require this kind of visa like I mentioned above.
You only need a visa if you wish to enter the country. You can leave the aircraft during the stop so long as you remain in the international lounge of the terminal. Just don't go through immigration (passport control).
According to the Department of Immigration and Border Protection, a transit visa is required "if passengers are required to pass through Immigration clearance and check-in to their onward flight, including managing their luggage."
This means that you do not need a transit visa if you are remaining on the same flight and it is only stopping in Australia to refuel before resuming its journey.
You would need a visa if: (1) you need to change planes, and in order to do so you need to collect your luggage and check-in again, or (2) the flight will remain in Australia overnight and resume in the morning as passengers may not remain in the airport overnight.
The page I linked also has a long list of nationalities which do not require a transit visa in advance in transit Australia. In this context, "transit" means to remain in the country for no more than 72 hours.