Frankly: I've got no clue, David.

What I can tell you is (short version): it's more than a year that I've heard first time about recruiting of hundreds of Kurds in Iran (and local authorities doing nothing against this, in some cases even being afraid of recruiters).

While trying to find more info about this topic, I somewhere stumbled over a report about Treasury imposing sanctions against specific figures in Tehran for 'supporting the ISIL'. Back then I was wondering about 'actual reasons' for such reports. But, in last few weeks multiple reports appeared about thousands of Kurds that have joined the Daesh. Many of these are supported by videos uploaded on YouTube by quasi-Turkish or quasi-Arabic members of the Daesh, with a distinct accent several people told me is 'Kurdish'.

In total, when I connect the dots and calculate all the numbers I've heard from sources anywhere between Diyarbakir in Turkey and Baku in Azerbaijan... I can't but conclude that about 10,000 of them have already joined.

(And that's my 'most conservative' estimate.)