I've posted this on Twitter. It's in response to Christoph Winterbach of Der Spiegel, who I've been talking to for a while.
Doing my response this way as that means I can do a proper thread. Let me try to clear this up as I understand it. FFP is clear that owners or related parties to them can inject funds via sponsorships. But the definition of a related party can be subjective. It's set out in the accounting standard IAS24 & City (and their auditors) maintain that none of the Abu Dhabi companies are related parties under this. If they were then the transactions would have to be specified as such in the accounts and they aren't. UEFA may dispute this.
If they were related parties then those deals have to be at 'fair market value'. The main Etihad deal was deemed to be FMV by UEFA so should be fireproof, regardless of where the money originated. So any issue is with the other sponsorships - Etisalat, Aabar & Visit Abu Dhabi. The argument is therefore presumably (a) whether these are related parties & if so (b) whether the deals are therefore FMV. If not (a) then (b) doesn't apply. UEFA's auditors claimed that they were related parties and they were overvalued. That might have to be tested in court.
As well as IAS24, UEFA have self-defined a related party as any entities from a connected source, eg Abu Dhabi state companies. These are not allowed to contribute >30% of total revenue and I believe they don't (it's maybe 20% at the very most). So that's not an issue either. So the core issue may be whether the other three companies are related parties under IAS24 & whether the deals are FMV. however if this only relates to the 2012/13 year then it's questionable whether UEFA could revisit the 2014 settlement agreement.
Your own articles said that UEFA knew of these deals in 2014 and had questioned them but we failed anyway & were sanctioned. The Galatasaray CAS ruling possibly closes the route of a re-opened punishment but there's the potential issue around source of funds/timing. If this additional funding carried on after the 2014 agreement then this may be a key issue for investigation. UEFA would presumably want to check whether it was disguised owner investment so would have to conclusively prove that these funds came from ADUG/Sheikh Mansour. As we discussed my firm understanding is that Abu Dhabi protocol means 'His Highness', when not followed by a name, refers to Sheikh Mohammed Bin Zayed (MBZ). 'His Highness Sheikh Mansour Bin Zayed' would be specified in the case of Sheikh Mansour.
I can't imagine UEFA has any power to compel any Abu Dhabi company to open its books so the investigation would focus purely on City. If UEFA can't prove that these companies are related parties or that the source of funds is ADUG then they have, in my view, no case. This is only my personal view based on my knowledge of the FFP regulations. I've had no input from City and have only seen the documents you've chosen to publish so it's also based on my reading of those.
There may be other avenues or issues for them to investigate but I have no knowledge of what these may be. I note that City have welcomed the investigation & I think it's needed to clear this up once and for all. The question is whether people will accept it if City are cleared.