News - Exclusive GTA IV content for PS3, too - source // PS3 /// Eurogamer

According to a source close to Rockstar North, the team is working on exclusive supplemental content for both systems, which will be made available for download via Microsoft and Sony's respective online services after the game's release next year.
And then theres this.

No exclusive content for PS3 GTA IV, says Rockstar - PS3 Fanboy

In the "news that blows" category, a Rockstar spokesperson confirmed the absence of any exclusive content for the PS3 edition of GTA IV.
Because the spokesperson said this nearly 10 months after the the first news im guessing there wont be any content on the PSN. I guess Microsoft won.