From an OZ who knows all about this stuff:-

But even if the cams don't always show up on the device, doesn't necessarily mean that the cams are not installed correctly. They are just incomplete, which is quite common. That's why they should only be used as a guide. And I would imagine NZ ones to be even more inaccurate than the AU ones.

So...assuming you have activated them (have the .dct in the map folder) and set up a warning sound, then what you have is all TT can offer