The blog instructions say to rename the car icon of your choice to 3dauto.bmp. A quick search of their replacement data.zip reveals the only reference to 3dauto.bmp is in their version of our navigatemap_800_480.ui where they have this section:
In our navigatemap_800_480.ui we have that layer but it is empty:
So I'm figuring that the other scripts in their data.zip are to suppress the 3d mdl icon, and replace it with the 2d bmp file. There's probably some scripting to ensure that the 2d bmp file is positioned in the right place, or maybe that's hardcode with the x214 y185 functions.
Edited to add: A closer look at the screenshot on that blog page does make me believe this is what is happening - the car icon looks like it's a 2d icon, positioned on the 3d map.

