A new interesting detail in a fresh NYT piece from Tehran:
The Expediency Council, headed by former President Ali Akbar Hashemi Rafsanjani, issued a statement that called the supreme leader’s decision the final word on the election, although it still called on the government to investigate voting complaints “properly and thoroughly.” The group also asked the candidates to cooperate with the government in any probe.
Mr. Rafsanjani, though a consummate insider, has been one of Mr. Ahmadinejad’s strongest critics and one of the most ardent supporters of Mir Hussein Moussavi, Mr. Ahmadinejad’s chief rival in the election. Mr. Rafsanjani’s son had even financed an elaborate system intended to check for voting fraud before the election. But since the vote, the former president has been quiet, and many Iranians were hoping he could broker some compromise behind the scenes.
So there was a "elaborate" and "well financed" system not under government control to check for election fraud. Moisavi had over 40,000 election observers in the field who must have reported to some central entity. Where are its results? What are they? Why were they not released?
If Rafsanjani would have proof for election fraud, why would he not leak it too the public or hand it over to the guardian council? Instead he now agrees with Khamenei on Ahmadinejad's victory.
Of course there are again various conspracy theories one might (and some will) develop around this. For now I will go with the least conspirishy one and assume that, in absence of any proof, there was no fraud at all.