Also, based upon the timing, I wonder if Danny *was* involved in discussions related to the trade. It wouldn't surprise me if Danny only bought Rasheed out when his role in this trade fell through.
I think Danny was involved in alternatives to this trade. Houston was known to want luxury tax relief, making them a team that might want Sheed's contract. They found a deal in which they actually got back a player they like in Courtney Lee. The Celtics really can't give them a better offer.
New Orleans wanted out from under Posey's horrible contract, but they wanted talent back, as well, to hopefully make Chris Paul less disgruntled.
Indiana was looking for a point guard, so the deal probably began as Indiana asking about Collison and the teams looking for additional trade partners to make salaries work out. Possibly, Ainge was looking at Mike Dunleavy as a 3 off the bench, which would require Sheed plus Baby and maybe some other things. Perhaps no team wanted Glen Davis.
New Jersey was looking to rent out cap space. They got Troy Murphy. Ainge may have been talking to New Jersey about using their cap space to get an exemption, but he would have to offer them something more useful than Troy Murphy. That also possibly gives you an idea of what other teams with cap space, like Minnesota, want in exchange for a trade exemption.