Chicago public art: bridge sign

I caught this shitty photo of some cool public art hanging on a fence bordering a road. I was riding by Chicago (to get to Rosemont) and saw this. It's a bunch of cool-colored signs. I forget what they said, but the look of the piece as a whole was neat. Does anyone know what this is and who did it?

Poster Boy: ripping up the Subway

Oct 3, 2008 New York Magazine article: "Slice and Dice: One man’s vandalism is another’s political art. Just ask Poster Boy, the Matisse of subway-ad mash-ups." Other links: IllegalBillboards.org, PublicAdCampaign.com