I don't think Iran expected Israels response either. But then again, I don't think they were looking for that.
I think they were looking for the UN to get a Lebanese force in place to assist the Hezzies with resupply and a buffer against Israel. Now, if Israel goes back into Lebanon, they will have to deal with the Lebanese army who will say that they are being attacked by Israel and this will be Iran's and Syrias excuse to join a war.
There is a lot going on here.
Doesnt make sense they are using hezz for a buffer not to get into to a direct confrontation. Any direct confrontation between Syria or Iran with the US or Israel would mean regime change in Iran and Syria, this is a suicide move if they try it. They havent been looking for an excuse to attack Israel so far, because they know they will lose, why would that change? One or two nukes I dont see it. Not yet.