I've heard of that on here before. I would doubt any 'actual' firefighter would not be allowed by their department to OC, but as for a volunteer in a rural area, I'm sure it's not that odd. They're people too, just trying to live through the day by OCing, and just happen to also respond to a fire call. No biggie.
As for the OC badge, I just think that the concept of CC/OC badges is wrong. Basically trying to make people unwittingly think you are a LEA as not to be bothered. Hard for me to articulate why, but it doing that type of thing just rubs me the wrong way.