This explanation is found here:
http://www.hornets247.com/blog/2012/07/ ... more-31332
Dell Demps has just provided clarity to the situation at hand regarding the legality of today’s trade. Because Brad Miller was received by NOLA using room under the salary cap (not an exception), they were allowed to trade him immediately with another player. Though it was unclear in the CBA FAQ, the Hornets being over the cap right now does not matter as long as the player being dealt was received at the time by using cap space. (We’ll ask Mr. Coon to include that in his excellent site for future reference.)
So, in the Brad Miller case even though the team was over the cap when re-trading him, they could aggregate his salary anyway based upon the cap status when originally getting Miller?
And by corollary/inverse, then if a team over the cap gets a player can they not aggregate that player without any delay period if, they drop under the cap? I.e. Say Orlando swaps Richardson for Brad Miller (just as an example so Brad Miller can keep going around). The next day Orlando completes a large trade and drops under the salary cap. Can they still not use Brad Miller to aggregate in a trade, even though they now are under the cap?