In rural EMS we use the criteria of risk vs gain to determine what's appropriate. There are a number of risks to carrying O2 in a POV. How often are you going to use it? How long is it going to be used before an ambulance arrives on scene. If it's not being used often, what is the system for getting the bottles refilled and hydro'd? How well can you secure it in your vehicle. If you are securing it adequately, how easy is it going to be to free up when you need it?
In order to authorize my vollies to carry O2 in their POV, I would have to see a rash of pts, unable to get O2 often enough to show a need to change our existing policy. It needs to be done to meet a need in the public, not to simply reduce the responder's pucker factor. What is your average response time with a unit to the pt? How long is the average time a responder is with a pt before the arrival of a unit?
If you look at the facts, chances are the risks and liabilities of carrying O2 in a POV are not worth the limited number of possible advantages.