So thats 8 regions each with 1000 access points excluding stub networks.

What is the maximum we could fit into Auckland?

If you chop Auckland up into 1000 square KMs, thats an AP for each sqaure KM.

Consider that I got a good connection to my AP from the hanger. The Hanger is 6km away, or covers and area of 36 square km. lets say that you might get say 10 AP's into that area in the future using all of 2.4 and 5Ghz spectrum.

Thats 1000/36 * 10 = 270 APs.

And there are 3 regions assigned to Auckland.