There are supposed to be units made up from Arab-extremists (Hezbollah types) that are augmenting the Mullahs' security forces. I don't think that these Arab battalions are going to have any problem slaughtering Persians in pursuit of some hardline Islamic theology.
The wild-card may be the Iranian Army. Whichever side that they come down on will win. I'm sure that the Mullahs are busily reviewing the 'reliability' of units in the Tehran area.
Wow. Something stuck on my clipboard from another thread ... apologies for not reviewing the post.