Problematic. Not only does it rest on a single source but both Shiites and Sunnis have reason to want it to be true, the former because Mughniyeh is a degenerate hero within their sect for his legendary jihadi exploits and the latter because having his fingerprints on the JAM ties it directly to the hated Iranians. If the source is acting out of sectarian motives — not far-fetched given that we’re talking about Iraq — then he’s got a motive to trump this up, regardless of which sect he belongs to.
Mugniyah helped form the Mahdi Army after the fall of Saddam Hussein’s regime in April 2003. He recruited from the Shia communities in Kuwait and Saudi Arabia, and then sent the recruits to Lebanon’s Bekaa Valley for training. “The 300 fighters were trained on the use of assault rifles, booby-trapping and kidnapping operations,” the unnamed intelligence official told Al Zaman.
Once in Lebanon, the Mahdi Army recruits were sent to bases run by Brigadier General Qassem Suleimani, the commander of Iran’s Qods Force, the foreign special operations branch of the Iranian Revolutionary Guards Corps. Hezbollah operates numerous bases in the Bekaa Valley, under the supervision of Syrian intelligence.
Read all of Roggio’s post for superb background on the Sadrist/Hezbollah connection. There’s loads of circumstantial evidence supporting it; like I said in the assassination post, it’s only logical that Iran’s number-one guy would be involved in building their new proxy in Iraq, especially given his spectacular success in Lebanon. “A natural fit,” as Roggio puts it. The only question is whether he played the initial Zarqawi-esque organizational role being asserted here.