The prospects going back for Burnett aren't anything special, as this is just a salary dump for the Yankees. Exicardo Coyones is a tweener outfielder, who doesn't have the bat for a corner, but doesn't have the defense for center. Diego Moreno is a pitcher with a lot of arm strength, but one who lacks command. Both of these players were available in the Rule 5 Draft this past December, but neither were picked up. There's nothing to be had with either of them, and they're only included because by definition, "trade" means something has to go both ways.
But Burnett going to the Pirates is actually very interesting. A pitcher who's made at least 32 starts in each of the past four years shows both durability and effectiveness. In this day and age of max-effort pitching, avoiding injury could be considered a skill, but also being able to make that many starts without being pulled form the rotation shows a talent level which is considerably above replacement level.