It is not plausible to me that they would deliberately hit the UN people, but war is messy and you simply cannot guarantee the safety of non-combatants in a war zone.
I think they would hit the UN people if they were artillery spotting for the hezbos. For world consumption they would have to pretend they didn't mean to.
This is a little bit like the USS Liberty. Politically they couldn't blast us, but if we were gathering intel that they had reason to believe was being used against them, they had no choice. There is a lot about that story that never came out, imo.