And by this, I mean, using the threat of withdrawal to compel on the ground reconciliation between Sunnis and Shiites. For those too lazy to hit the link and read some long boring article by the Washington Post, the upshot is that Sadr has ostensibly begun to purge elements from his leadership who express a generalized hostility to Sunnis rather than to Al Qaeda specifically.
This strikes me as a rather transparent sop to the West -- we shouldn't assume that he is saying the same thing to an Iraqi audience, nor to an audience of loyalists. I think he is seeing the inevitable end of the Weimar, er, Al Maliki government, and is positioning himself as something palatable to the West upon withdrawal. So, no, its no guarantee of the behavior of the Mahdi army, or Shiite loyal elements of the police forces in Baghdad. But it still shows at least one significant development -- Sadr cares who the Prime Minister is. Nothing could be more dangerous than the localization of sectarian politics in Baghdad