The 'Iranian-backed militias' in Iraq are otherwise known as the government of Iraq. They get their weapons largely courtesy of the USA.

I find this quote hyperbolic and not particularly accurate. But it's still 1000x more arguable than the title of this post.

First, the article is citing a study using data from a certain time period:

The database was compiled by MNFI's Task Force Troy, which was directed to examine all weapons caches found in Iraq beginning in early January 2008 to identify Iranian-made weapons.

As publicly noted by many senior US military officials at the time, the quantity of EFPs, etc., significantly and drastically dropped off around the same time violence started declining (Summer-Fall 2007). Whether this was due to targeted US interdiction of Iranian ratlines or a deal the Iranians made with players in Iraq, it happened, and US military officials at the time noted its surprising, rapid decline.

A couple of other random data points: the US military has specifically interdicted EFPs and rockets being imported from Iran, and 9 Quods Forces operators were arrested just in the past month coming into the country. (There are many more data points of this nature)

EFP technology was initially imported from Iran - its use is limited in captures and geographic area corresponding with Shia militias, and Mahdi militiamen have gone on record with the LA Times indicating that they were receiving assistance from Iran.

Subsequently, EFP factories have been found in Iraq. By the logic of this post and article, does that mean that the technology and know-how didn't come from Iran because they were subsequently manufactured in-country? Is it a "myth" being made up by the military, because small proportions were found in sweeps post Jan 2008, 5 months after US officials were noting staggering declines in EFP cache finds and attacks?

As to the proportion of weapons with Iranian manufacturing stamps on them, in isolation, this only reveals that a certain proportion of Iranian-manufactured weapons were in Iraq (during the timeframe of the analysis).

Drawing the conclusion that all arms supplied by Qods Forces to Shia militias in Iraq will necessarily be hot from an Iranian weapons factory is an assumption. Qods can very well be savvy enough (as Western intelligence services) to mix up the supply to avoid generating casus belli against Iran (not that evidence of Iranian weapons would generate casus belli, at this point).

Extrapolating this to deny the fact that Iran has been funneling men, know-how and material into the country is a rather large mistake. Debate the quantity - but beyond that such any sweeping denial is objectively incorrect:

http://www.longwarjournal.org/archives/2007/12/irans_ramazan_corps.php