Nice google, but you need to look a bit deeper. Trust me, they don't get off for free and will have to pay to get his shit fixed...
"One of the more common exceptions to government immunity (where the government may be liable for its actions) is vehicle liability, when government employees are involved in auto accidents. These typically include emergency vehicles, such as police car pursuits, fire trucks rushing to a fire, or ambulances rushing through intersections to get to the hospital. Non-emergency accidents are also possible, like being rear-ended by the public school bus or side-swiped by a city public works landscape truck."
http://personal-injury.lawyers.com/auto-accidents/government-liability-for-auto-accidents.html
http://www.reminger.com/upload/banners/PUB-01032011.pdf
http://accident-law.freeadvice.com/accident-law/auto/government-car-accidents.htm