I think we have gone as far as we can and are moving from the general to the contractual. It does appear that you have a (contractual) dispute that can only be resolved using the normal methods (between the parties and out of the public view).
To conclude the discussion - in my view:
The ICAO Convention and SARPs are applicable only to States - the preamble to the Convention states:
"THEREFORE, the undersigned governments having agreed on certain principles and arrangements in order that international civil aviation may be developed in a safe and orderly manner...".
My understanding is that each State has to provide regulations in compliance with the Annexes (and make a statement to that effect); if there are differences (and there usually are), they must be declared to ICAO - these are then Appended to the Annexes to which they apply.
To my knowledge, the only Annex that
may be directly applicable is Annex 2 'Rules of the Air' - and then, as specified in Article 12, only "Over the high seas...".
It would appear therefore that the words that you have quoted are based upon a misunderstanding of the extent of the 'ICAO remit' and the intent of the Convention. With the exception of the case above, there are no 'applicable ICAO regulations' (in fact there are no ICAO regulations, only the Convention and SARPs - and of course various guidance papers).
If you wish to seek an answer to the question on the age 60 rule, you have to look to the FARs and the local regulations and, more importantly, the contract. If a State (or contractor) wishes to provide a set of regulations for a type of activity which can be regarded as 'State' under Article 3 (the UK police are a good example), it can take whatever template it likes. If those regulations are based upon (say) the rules provided by Parts 91, 119 and 135 and it is shown that one, or some, get in the way of the operation, they can, and will be, alleviated.
Jim