Article 8 of the Aircrew Regulation states that the hours requirement for ground and flight training is waived if he holds an ICAO licence.
Not quite. What Article 8
actually says is that the credit given shall be determined by the Member State to which the pilot applies on the basis of a recommendation from an ATO. Rather than just training as required, the ATO is required to recommend a course of training to the CAA, which will then decide whether to approve it.