Other mistake: On the second day, Phil did his same tasks at about the same time as the previous day, so everything lining up the same made sense. However, on day 3, he quickly rushes out of his hotel, avoiding interacting with most of the people he did before and gets to the street with the beggar much sooner than he did before. Yet Ned still is there crossing the street and sees him exactly the same as before. However with Phil having skipped so much he would have gotten there and passed that spot a good while before Ned would have gotten there, and they should not have had the exchange again on day 3. Same thing for when he arrives at the Groundhog Festival, with Rita greeting him like he's late. But he would have gotten there much sooner this time.
Other mistake: Focusing on the clock as it turns to 6:00, one clock has a visible gear in the middle of the numbers. At other times, no gear.
Other mistake: In the opening scene as Phil is walking from the blue screen to the desk, a clock is visible over the top of the camera and it reads either 12:20 or 1:20 (the hour hand is too motion blurred to tell which). The broadcast is supposed to be at 5pm. (00:01:40)
Other mistake: When Phil is driving the car against the train he ultimately swerves out into a railroad crossing. However when the approaching train is shown from within the car in the last seconds before the two vehicles would collide, there is no crossing to be seen on the remaining track stage between them.
Answer: We know the police car survived because unit 2 is the car that followed them onto the tracks, and unit 2 is also one of the cars present when they are stopped (though it came from the wrong direction). The movie doesn't explain how the car survived so it is left to the viewer's imagination.
jimba