I just did a quick test getting Excel to generate 130 random numbers between 0 and 100, 4 times over. In all instance the most common number appeared 4 times or more (4, 6, 5, 5), in all cases there were numbers that didn't occur at all. It's entirely possible to get 5 of the same car and none of another car and it still be random, and the fact some people have dupe Citroens but no P330's is evidence of nothing.
Having said that, I don't think it's entirely random either, it wouldn't surprise me if the probabilities were weighted one way or another, or seeded by in game actions. Maybe I virtually never see the 20,000,000 cars on the wheel at all because I've not completed any tier of achievements in Sport Mode (for instance).