Exactly. I don't see the need for him to chase the ambulance down in a pseudo cop car. On the other hand, there aren't many people whose feelings would be hurt by Southern California ceasing to exist.
If he doesn't know how to get a hold of his crews by either radio, phone or nextel, speeding ambulances are not his only problem.
Right or wrong, as you said before, 15 MPH over may not be that uncommon for any vehicle traveling that stretch of road.
Also, the story stated he traveled as high as 14 MPH over the speed limit according to GPS. It's possible that speed was obtained for a short amount of time. I'm not familiar enough with GPS tracking to say how reliable they are at assessing speed. I've had my personal GPS go down below the minimum of tracking satellites and lose direction.
If he was operating outside the company's guidelines (which it sounds like he was), then yes; he needs to be disciplined.