I haven't been following the Shahram Amiri story very closely. It has seemed to me that none of the stories are believable. So I don't have the back story down in any detailed way. A week or two ago, dueling videos showed up, apparently from the same person. And now he's back in Iran. Unless a double has been substituted for him.
There are lots of stories like this that I don't follow very closely, largely because they aren't central to my interests and it looks like untangling them will take more of my time than I can give to them. Juan Cole and Gareth Porter have developed coherent possible story lines.
I'll add one more layer to those possible stories: What if the CIA, in accepting Amiri's offer, was entirely aware that he could be a double agent and was just checking him out? That would mean that any information he offered would be considered not credible until confirmed in some way, but even a made-up or exaggerated story might provide some lines of investigation. The wrong lines, of course, would be part of the purpose of a double agent, but the CIA would be aware of that possibility. We don't know what use, if any, has been made of the information he offered up.