Being a firefighter and also in EMS, it is my opinion that a 911 EMS unit should not do rehab. Of course though many areas simply can't do any better. A 911 should be available, but not obligated to to rebab. Many places have specified rehab units packed full of water and coffe, small snacks, etc etc.
Each time a firefighter comes out of the building, or appears to be tired, which should be noticed by a rehab officer, that person should be evaluated. Simple vitals taken such as BP, pulse, pulse ox (yea i know fire.. smoke CO, false readinds and all that mumbo jumbo).
I have seen too many times, a person coming from the fire, sweating like crazy, getting a new air cylinder, then going back in. It's bad all around. No control from officers if you ask me. Firefighters aren't super heros, no matter how much they think they are. Human just like everyone else. Take care of yourself, officers look over your crew!