Question: Cost of NYC2012 Olympic Propaganda

pro-olympic ads are all over new york city. they're on the taxis, subways, streetlamps, etc. who is paying for all these ads? if the taxpayers are, what is the cost of these ads? how did the city get the ads into taxis? is there any fair use or requirement of balances to taxpayer funded propaganda if a significant segment of the taxpayer base doesn't want the policies?