Night vertex only works for skins and cars. It doesnt work for map objects afaik.
Even if it's only the model that can be turned on/off you can still apply another texture to it after turning off and then on. I believe that's how GTA III does it when it's night time on Stauton Island near the "Times Square" imitation.
Or they simply make a copy of the object and apply the brighter texture to it, replacing the daylight model.
Nope. Night vertex works for all .dff's. If they were to have 4-5 copies for each object with a darker texture each time then re-texture mods would take extra long and the game size would be much larger.
Hmm. Then why dont neon lights aren't reflected in the walls (im talking about the neons added in SA-MP for cars).
They reflect on peds and cars but not on solid objects like ground and building walls. Perhaps night vertex isnt enabled for those objects?