Once a waiver claim is made, the claiming team can trade anyone they want (and the other team will accept) for the player. However, whoever the claiming team trades must also have passed through waivers as well, or another team can claim that player. For instance, let's say the Cubs claim Juan Cruz. Once the claim is made, the Royals have the option of pulling him back, letting the Cubs have him and his salary or working out a deal with the Cubs. Assume they go with the third option and a deal is worked out for the Cubs to send Miles to KC for Cruz. Before that deal can go down, though, Miles must pass through waivers. If he does, the deal happens. If he's claimed by someone, then the Cubs have the same three options with Miles the Royals had with Cruz. The Cubs also much then either figure out a three-way deal, or work something else out with the Royals for Cruz. I'm pretty sure that's the way it works.