Vanilla Vehicles Expanded Tier 3 wreck spawn rate

Does anyone know if the spawn rates of the various tier 3 wrecks are the same for each type? I’m trying to find a wreck of either of the helicopters but all I seem to find are the land vehicles, and primarily the classic car, super car, APC, humvee, and artillery.

I also notice the loading screen mentioning vehicle regions. Do certain parts of the world map spawn different wrecks?