Related: Notice that ever since Ahmadinejad took power in Iran, and made Mughniyeh his defense minister, Iran has been very actively founding Iranian-controlled terror groups in as many places as possible: AaFaA Brigades in Iraq, its old Hezbollah setup in Lebanon and Syria, its infiltration & takeover of Hamas in Gaza, etc. If I were running a government anywhere vaguely in that region that had a Shi'ite minority, I'd be keeping my eyes open for whatever satellite group Iran were setting up there. And note that this is an international network of professional terrorist groups with the systematic sponsorship, supply and control by a government that's trying to become a nuclear power: the worst hypothesis is confirmed.
Iran is gearing up for a major proxy war. If they set up these units in every Middle Eastern country with a Shi'ite population, they could effectively destabilize the local governments and install friendly regimes, or at least create friendly circumstances "on the ground:" the true creation of an Iranian sphere of influence. The other thing these teams are for is for fighting against the US/Israel alliance, which it views - quite rightly - as a competitor for geostrategic power in the region. Such a force would certainly back even non-Shi'ite groups to further its aims; (remember that Iran supplied weapons to the [Sunni] PLO for years) direct alliance with groups like al-Qaeda is less likely, since those groups have very strong ideological leanings which aren't that compatible, but these guys have the potential to be much more strongly unified.
The question of just how broad Iran's ambitions are is open: they want this network, they want ICBM's (they already have intermediate-range ballistic missiles, like the Shahab-3; once North Korea finalizes the Taepodong-2 ICBM, Iran will probably be the first customers), they want the Bomb. Do they want to take on China or India for regional power? Would they want to press engagement with US/Israel even beyond the scale needed to push them out of the area?
Another interesting question: How will Russia come down in this? They haven't decisively allied with either the US or Iranian side in this conflict, and have been willing to work with both. At some point it will probably become very difficult to do this. Which way it goes depends e.g. on how Iran decides to involve itself (or not) with Chechnya, but it could have a big impact on how much free rein Iran ends up getting in the Central Asian sphere.
