According to the Washington Post the kidnapped sheikhs were mixed Sunni and Shia and were taken by the Mahdi Army (Sadr's band of idiots). That at least makes it possible that they may be released alive. Sadr has to exist in that environment I can't imagine he wants the tribes too angry at him.
The Shiite and Sunni sheiks, members of the Al-Salam Support Council, a group fighting Al-Qaida in Iraq in volatile Diyala province, were taken from their cars by gunmen as they returned home from a meeting in Baghdad with a government official, the tribesmen said.
Hadi al-Anbaki, a spokesman for the mostly Shiite council, said the attack was carried out by the Mahdi Army, a militia controlled by the anti-American Shiite cleric Muqtada al-Sadr. "This was an ambush," Anbaki said.
The kidnapping highlighted the complex and quickly shifting nature of the bloodshed convulsing Iraq, with Shiite and Sunni groups increasingly targeting members of their own sects who align themselves with U.S. forces.
(Note: 15 of those 53 were decomposed bodies found by US forces while engaged in anti al-Qaeda operations so maybe I am making too much of this.)
Iraq, War, al-Qaeda, Mahdi Army, al-Sadr