The Artesh (Iranian regular army) has been purged & cucked to death by the Islamists since Khomeini's revolution, he basically did a Stalinist purge of their ranks after taking power (which weakened them so badly that Saddam dared to attack Iran in the first place, back in the day) and the Mullahs have in general been very very careful to keep them under control & weaker than the more loyal IRGC ever since. My understanding is that you basically have no chance of getting promoted to any post of relevance in the Artesh if the Mullahs aren't 1000% assured of your loyalty and even their current top general,
Amir Hatami (also the first Iranian defense minister in ages to have come from an Artesh background instead of an IRGC one), had to have joined the Basij Islamist paramilitary in his youth.
Individual soldiers and maybe even small units might defect, but I doubt we'll see any large-scale fracture or mass defections by the Artesh until later in the game, if the revolutionaries continue to gain momentum.
