Another thing I should mention are the roadside emissions tests, which if your vehicle fails, you get a letter telling you that you have 30 days to go to an emissions testing station where they'll not only do an OBD-II scan, they'll put it on the dyno too. On top of that I think (not sure) that they randomly do dyno testing of vehicles. The guy at the emissions inspection station said that the computer sometimes tells him to do a dyno test too. I had wondered why they still have the dynos and asked....
(I do know that they (Dept of Environmental Quality) have a list of vehicles more likely to have a high "vehicle emissions index" and the vehicles with the highest VEI tend to be the ones you'd think would be the most likely to get a cat delete, like Mustangs and Civics).
Maryland got rid of their Dyno's a few years ago. I know this for sure since I had a 1995 car at the time so no more emissions test on that vehicle.