What makes you think that the Iranians were involved?
I presume that the cell is AQ-affiliated and composed of local Pakistanis and/or North African immigrants.
[What makes you think that the Iranians were involved?]
It doesn't matter. They're next. You defeat Islamism by democratizing country after country. This attack must be answered by at least one major regime change and it doesn't matter which one (actually, it matters to us to get the one with the most oil money still going to terror groups and that is Iran). After a while, they get the message: no more dictatorships. Unfortunately, we didn't do a regime change after the Madrid bombings. That guaranteed the London bombings. It is common sense. The left wing forced us to slow down the war until this happened. God help us if we remain in the "slowed down" mode.