I think there is a danger of over-complicating things here. I know people are arguing for a full Annex 13 investigation into this event but I don't think one is either likely or necessary.
The primary purpose of an Annex 13 investigation is to determine the cause of an accident (or incident) in order to prevent a recurrence. Unlike MH17, there is no need for a forensic examination to prove the aircraft was shot down and identify the type of missile involved because the Iranians have publicly acknowledged the aircraft was downed by a missile, albeit in error; there is nothing to be gained from a safety investigation per se.
The type of missile is also not relevant from a safety perspective - nobody is in the business of certifying transport aircraft to withstand a missile strike, so there is no point in trying to work out the details.
Having 'owned' a live missile engagement zone in a previous life, my own view from the outset was that this had a failure of command and control written all over it. Different nations have different systems for controlling such things, but all will have some means of limiting the potential for own goals or targeting of innocents even if that is only via basic aircraft recognition. There certainly needs to be an investigation, and it will be an Iranian investigation to find out what part of its system failed: was it someone over-reacting or simply leaving a switch in AUTO?
I doubt very much whether there will be full (if any) transparency, and you could not blame them for that - most governments would do the same. While it will not bring people back, at least the discussions on compensation will start from an admission of liability.
Separately, there is work to do for ICAO. We need a better process for ensuring that commercial air transport flights are not placed at un-necessary risk when operating near conflict zones. Arguably, the fact that ballistic missiles were being lobbed about the place and that someone had offered to send cruise missiles to 52 targets of his choice should have raised a warning flag.
Let's see the ICAO security panel reconvene to review the lessons from MH17 in light of this latest tragedy.