Is it possible to add custom POI lists (such as a file with all the Harley Davidson dealerships, or red light cameras) to the Z2?

Nope, it's not officially supported, and nobody has hacked it yet.

What I did was when I was at a intersection where there was a red light camera I touch the screen at that intersection and then you will get the little red circle and on the right side of the screen you will see a menu there you can add it to your adress book and I put the icon of a camera and the sound of a camera from the options you get. So now when I get near that intersection I will here the sound of the camera as a reminder.