I suspect he has Rove's cooperation. Will Stephen Hadley or someone else supply the final nail in the Cheney coffin? Or does Fitz need Libby -- which would mean he has to wait until either Libby is convicted and his appeals are over, pardoned or acquitted in order to force him to testify? (Those are the events which would cause him to no longer have a 5th Amendment privilege since nothing he said afterwards could be used to incriminate him.)

Also from Murray's article:

Then-Attorney General John Ashcroft continued to oversee the Valerie Plame-CIA leak probe for more than two months in late 2003 after he learned in extensive briefings that FBI agents suspected White House aides Karl Rove and I. Lewis "Scooter" Libby of trying to mislead the FBI to conceal their roles in the leak, according to government records and interviews. Despite these briefings, which took place between October and December 2003, and despite the fact that senior White House aides might become central to the leak case, Ashcroft did not recuse himself from the matter until December 30, when he allowed the appointment of a special prosecutor, Patrick Fitzgerald, to take over the investigation.