The major problem that we had with illegal vehicles/driver here was unlicenced drivers who were driving legitimate cabs. Back in the Zone Days, the test for the hack face was not easy. People regullarly had to take it three and four times. Some people never passed it. I actually passed my first try, but, had I answered one more question incorrectly, I would have failed. The scenario here used to play out (and still does, but far less, since Uber/Lyft):weekly rental with a partner
These four guys would all go at the same time to write the hack test. Eventually, one of them passed. He went through the process and got his hack face. He then went to the offices of this one large fleet operator and asked to rent a cab. The guy had his hack face and his money, why not rent him the cab? So Mr. X pays his money, goes out there and works the cab six hours. He then goes to the parking lot to pick up cousin Y. Cousin Y, like all ot the rest, has no hack face. Only Mr. X has a hack face. At any rate, Cousin Y drops off Mr. X at home and works the cab for six hours. Cousin Y then goes to the hotel to pick up Uncle W. Uncle W, with no hack face, drops Cousin Y at home, then works the cab for six hours. Uncle W then goes to Brother-in-Law Z's home, picks him up, drives to school, gets out and Brother-in-Law Z then works the cab for six hours. Finally, Brother-in-Law Z goes to the restaurant, picks up Mr. X, and the cycle starts anew.
The cab is going twenty four/seven/three-sixty-five with days off only for a major Ethnic Association Event, graduation, funeral or wedding. Mr. X does have to go to the office every week to pay the rent and must be the one to take it to the shop if it needs something. If it breaks down on the street, whoever is driving calls the office, which sends the tow truck. The driver is instructed to leave the key in the ashtray, on the right front tire or under the floor mat up front. Of course, when the car is repaired, Mr. X must go to fetch it. The shop foreman does not care if the car is coming in more frequently than you would think. Everyone knows that this fleet operator rents out mostly hoopties, anyhow, so if he cares at all, which he usually does not, he does not think that it is out of the ordinary.
Where it breaks down is if there is a collision. At that point, if the wrong guy is driving it, there is trouble. The cab company gets the Police Report and sees that the driver is not the one assigned to the car. The cab company tells the insurance company and the insurance company denies coverage.
The other possibility is that the hack inspector stops the cab when the wrong driver is behind the wheel. At that point, the cab gets impounded and, if the hack inspector has a bug up his [donkey], he issues a summons not only to the driver, but also to the owner for permitting an unlicenced operator.
This does not happen as much as it used to happen, Uber/Lyft are largely responsible for this as well as a former Chair of the then-Taxicab Commission, who had his hack inspectors go after illegals. At that point, the unlicenced drivers thought "Why risk it"" and went to Uber/Lyft. The illegals were actually the source of most of the problems that the riding public had with the cabs. When UberX and Lyft came, as the illegals parked their cabs, the complaints against the drivers diminished markedly. These former illegals did take their bad habits with them to Uber/Lyft, but m ost of them have not been de-activated Y-E-T.