I commented on this a while back.
Reading this article gave me an idea. Perhaps the next market for JC Decaux is public cell phone booths. These could be similar in design to the bus stop shelters - clear glass on 3 sides (one being a door) with advertising on one side. They could charge a quarter for 15 minutes to give people a place to take a phone call in places that are otherwise too noisy and/or crowded for it. Think there's a market for this?