I commute on transit and in my experience, those that can't afford transit simply don't pay the fare, so I'd guess impact would be pretty limited for those that might benefit the most from free transit. They either hop on via the back of the bus on the second set of doors away from the driver, walk directly onto the train platform without tapping up a fare card, or for the few stations that do have turnstyles, they use the emergency exit gate which says is alarmed, but in fact is not and swings open freely.