I live in Montpellier France and all transit has become free 2 years ago. I didn't notice any change in people's behavior at all. Transit is also free in Talinn IIRC and I wonder if they saw something there?
Then you'll ask for receipts of what they pay to use the roads and they'll be out.
Regarding free transit, I think part of the reason it can fail is the socioeconomic situation. In places that rewards the rich and abandon the less fortunate, it's deemed to fail.
But also, I think that when people have to pay to use transit, they'll be less willing to act as a warden, so if they see someone doing something negative, they'll keep out, thinking that it's the responsibility of whoever is taking their money. Meanwhile, when we see public transit as a common good, we are more willing to act to keep it great.
The maintenance cost graph is very eye-opening.