Voting has nothing to do with COS18. It applies, in some form and variations, to all Conditions of Service before COS18. If you read COS18 it clearly states that agreements with the HKAOA will not become part of the contractual terms of your employment unless ..........
Basically it is up to CX to allow the HKAOA to negotiate for officers on COS18. COS18 consists mostly of policies which can be amended at the companies discretion from time to time.