You know, in most states it's illegal to follow within 500 feet behind an emergency vehicle when it's running code (with full lights and siren), unless you are in another emergency vehicle which is also running code. If I remember correctly, here it's one of the worst traffic citations you can get (which means you can have your license suspended).
Anyway, when I was a police officer the only memorable time we got behind an ambulance was one time on the way to the ER. The city police had gotten into this fight of epic proportions with this huge mammoth of a man that was all hyped up on beer and liquid-X. We were there just to help out, just in case he got loose again (you'll understand why in just a second).
When they opened the door to the ambulance at the ER, out came the gurney with this huge guy on it, face down, handcuffed, nylon straps down his back and legs (keeping his securely on the gurney) with an EMT sitting on his back.
As the story was recounted by one of the police officers, the fight lasted for at least a good ten, fifteen minutes. The third time they shot him with the taser, he looked down knocked out the probes like he was swatting at some flies on his chest, that's when they knew they had a problem; I've known lots of instances where people shrugged off pepper spray. Some people are practically immune without the benefit of drugs or alcohol. But shrugging off a taser rates up there with one of those things you may never see as a police officer.
Anyway, eight police officers and three EMT's later, they had the big guy all strapped down and ready for his ride to the hospital. When they got him inside the hospital, the staff gave him something to take away his high. He started moaning and then the doctor came in and said, "In a bit of pain? I imagine so. I'm told you had a really good time tonight."