Most were taken off the streets and had their rusty license plates seized. The cabs' owners didn't want to do what everybody else does in Hamilton County, spend some money, wait in line and have their emissions tested. To keep the air clean. The cabs were registered in Brown County, where car registrations, like eggs, are cheaper in the country. Cheaper by at least 20 bucks than in Hamilton County.
Brown County is also a cheap place to have a heap that pollutes the air.
That county has no emissions testing. Hamilton County does. A cabbie can make that, and more, with two runs to the airport. It's always about the bottom line. Always has been.