I still have some also.. but thats not all why it crashes... it was better before in beta.Don't make that the end all cause though, I have a high end computer and still had CTD issues.
i got this from raf and dyson.. just spreading the msg.I'm not sure if I know how you got to find that out, considering there is other mods with much more units and scripts available that does not CTD as easily. Have a look at Norway Mod, that modification has more units and cars yet a very stable release. I think you should rerun your debug-logic and see if what you just said is correct as I think it's highly unlikely that is the reason.
Also, we know for a fact that certain scripts would cause the fire trucks to spin around like crazy. And that has nothing to do with the amount of models/units in the game, that is just the scripting of certain functions that has not been done properly. (That would cause a CTD aswell)