NHTSA says otherwise. http://www.nhtsa.dot.gov/cars/problems/studies/CrownVic/Index.html
"PROBLEM DESCRIPTION; The fuel tank can rupture following a high- energy rear collision resulting in severe fires. A vehicle occupant surviving the impact trauma could be killed as a result of fire intrusion into the passenger compartment."
Also, the crash tests that generate those star ratings are done at speeds below what the people being rear-ended are seeing (read the report at the link). More from the report: "ODI Findings:
* The crash energy levels associated with post rear impact fuel tank failures in the CVPI vehicles are significantly greater than the levels in FMVSS 301 tests.
* Fuel tank failures during high-speed rear impacts can result from numerous causes in addition to the hex-headed bolt and U-brackets identified in the Ford TSB. Crash reports identify many causes for loss of fuel system integrity during a high-energy rear crash, such as puncture from a deformed frame rail, lower shock absorber supports, or stowed items in the trunk, hydrostatic rupture, and other causes."
They also go on to note that the B-Body was just as bad - but IMHO that's okay because GM hasn't sold a B-Body in over a decade. Here are some other data points and a reference site: http://www.crownvictoriasafetyalert.com/timeline.html
Ford's own study shows that non-police CV cars are statistically more likely to go on fire than the competition, or even their own Taurus:
