I was trolling old forum threads and found this, figured I'd put in my two cents.

SIIC (formerly SCIRI) is in favor of a Southern federal zone. Dawa, the Mahdi Army, and the clerical leadership in Najaf are all opposed. The whole dispute is over money -- not oil money, pilgrimage money. SIIC controls Basra, they want to control the lucrative pilgrimage cities of Kerbelah and Najaf. That money currently goes to the Mahdi and those loyal to clerics like Sistani. Everyone other than SIIC all oppose the southern regional zone because they know that SIIC will control any sort of multi-province zone based out of Basra.

Basically, I don't think the Hakims are going to press the issue here -- they risk angering Sistani, and he is a huge wild card in any political calculation. I also think that SIIC generally doesn't want to risk pitting the Badr Organization against JAM if they can avoid it, and there's no way Sadr would go down on this issue without a fight. (I understand that gov't vs. JAM often is really just Badr vs. JAM in disguise, but I'm talking about all-out open street warfare, rather than the pin-pricks they're giving each other now.)