Such a sideways deal is very much like what BC did with Jones for Dixon. You have players who are not bad per se (although I happen to think that Joey will not play in this league past his current contract), they are just with the wrong team. Since cap implications are pretty insignificant for both teams, it's one of those "why not?" deals that are easy to make and that could just pan out.
BTW, I completely fail to see why GS would want to do this deal other than to accomodate Pietrus. Maybe they want Graham to play an undersized 4?