My point in mentioning Hezbollah was to demonstrate the fact Iran openly funds and supports known terrorist groups. I don't think it's out of the realm of possibility for the same regime to provide aid and comfort to an individual/group like Bin Laden and al Qaeda. It certainly wouldn't be difficult, from a logistics standpoint. Afghanistan, Pakistan, and Iran all border on each other.
I would not be shocked if they helped him in some ways. I would be surprised if they let him live within Iran's borders.