There was a time when if you suggested that the Iraqis made poor soldiers, impossible to train or motivate and unlikely to "stand up, as we stand down", then you were a racist or not paying attention to all the progress being made. Now, if a group of Iraqis show an incredible amount of planning, tactical and weapons sophistication in pulling off a daring raid, then they are either Iranians or trained by the Iranians.
I don't know who pulled off the Karbala raid and I don't rule out Iranian involvement, but reading Thomas Ricks book Fiasco has impressed upon me that you can't entirely discount the Iraqi insurgency which has shown unacknowledged levels of operational and tactical sophistication that has never adequately been explained to the American people by the Pentagon except in the increasing numbers of US dead. Given the bent of the White House and Pentagon, I'm not surprised they are quick to point to Iran but what happens if we're talking about some rogue interior ministry or Iraqi special ops troops trained by us? Spoke some English? American uniforms? Knew our security procedures and how to exploit them with a little inside help? I'll wait to see the evidence but it seems that scenario isn't entirely improbable either, is it?