I have worked for two companies driving Type IIs ("vanbulances") and one company driving box-type units (not sure if they were technically I or III, I always get them mixed up). Here are my thoughts.
In a Type II, I have noticed that the vast majority of other drivers seem to have very little or no respect for me. In other words, to them I'm just another vehicle in their way which they have the right to cut off, pull out in front of, and drive stupidly around just like they would with almost any other vehicle.
The company I worked for that used only box units just bought used ambulances from whatever municipal FD was selling them for cheap, and to further reduce the cost, this company didn't repaint them. I believe the selling agency removed all decals identifying the ambulance as belonging to a particular county or fire department, and the company I worked for added decals identifying the company, and that was it. Consequently, almost none of their ambulances looked the same (the few that did were bought from the same department at once), but most looked like they belonged to some fire department, more or less.
When I left this company and went to work for one with Type IIs, I suddenly noticed a marked difference in the way other drivers drove around me. In other words, other drivers seemed to drive a bit more respectfully around the box units. Now this could have been because maybe people just see the body of the Type II and just think "van" and don't realize "ambulance"; maybe it has nothing to do with the paint scheme. Or maybe it does have to do with the fact that the box units looked like FD units. I just don't know.
But I suspect that the paint scheme does have something to do with it. I suspect this because I have observed the same thing happen inside hospitals. When an EMT goes up to the nurse's station in an ER and he or she is wearing a private company uniform that looks nothing like an FD uniform, he or she is virtually ignored, but when someone goes up to the station wearing an FD uniform, or one just like it in the case of one or two companies around here that have the basic navy pants/light blue shirt uniform, they do
not get virtually ignored.
So, it is my theory that the uniform or the vehicle appearance does have an impact on how we are treated. Since I would prefer to be treated with a bit more respect, and I would like other drivers to drive with a bit more courtesy around me, well frankly I don't care if I have to cheat and disguise myself to resemble an FD to do it. So I voted for the "no but I'd like to" choice, so far I'm the only one.
But that's my 2¢.