This may signal Guard reluctance to fire upon their own. The economy in Iran has been so bad for so long that many men joined the Guard as a way to earn a living. Those recruits, the ones gained in the last five years, may also share this reluctance and are great enough in number to break the Guard’s ranks, allowing the popular revolt to touch the mullahs. Fascinating.
Also, if Guards desert, taking their arms and ammo with them, then it's a whole new ball game.