I think the evidence needs to be provided to CAD to return to work using your HKG license. I am sure the pilots in question provided any evidence needed to the new authority that governed their license. Probably amounted to an explanation and standard medical exam to meet class one standards.
eg... I was exhausted due to the rostering on the 747 at CX, I was stressed about the constant attacks from management. I was not fit to fly and would not be fit to fly under that pressure and scrutiny so went sick for three months, management are vindictive and it worries me. My new employer is great and I feel no pressure, am excited to get started.
Your right, Drs value their license to practise, any sensible one would not force a pilot to go to work if he is feeling exhausted and under pressure.