To sum it up: the bike system is operated by an advertiser, who is now using negative PR to strenghten his position in negociations with the city of Paris.

Why on earth is an advertiser operating bikes?

The city of Paris lets him use its outdoor displays for free. It seems the only advantage for the mayor is that he can claim the bike system works at no cost. This is probably the reason why he lets the advertiser keep secret the amount of his revenues from the displays. That barely honest financing scheme looks like the main problem.