In NYC the taxi commission is in the pocket of the medaillion holders. That's why the recent law to issue more mediallions (2,000 at ~800k each = $1.6b for the city) had to go through the state instead (Albany being less corrupt than anything is mind-boggling), until of course a judge knocked down the law and said only the city could do so.
Only source I could find about revenue is how they added $9.9 million in revenue by increasing the surcharge by 50 cents and recently awarded a $35 million dollar contract to Verifone.
So they must be generating some significant amount of money still.