[QUOTE]
But how is that policy documented and policed to ensure a level of quality assessment rather than a box-ticking process?/QUOTE]
The requirement is part of the FAA approved 135 Training program and requires a demonstrated level of proficiency at an initial and recurrent basis with the associated 135 training record.
but unless you have been tested in an environment (real or simulated) that replicates IIMC it is simply paper-safety ie no use at all. It is quite easy to replicate a DVE situation at night over unlit terrain or by day over the sea with hazy conditions, you don't actually have to go into cloud - but that is the real acid test.
How it is demonstrated is based on the the approved program and how the aircraft are equipped. Most use aircraft in simulated conditions but some operators have started moving into simulators for some of the requirements. However some don't pass either. We had a couple at the old day job that upgraded to a different airframe but couldn't get out of the clouds during the training. They both went back to the original rides until they got more training and eventually successfully upgraded again.
What I always found ironic was that even with the same identical training the percentage of offshore ops having adverse IIMC incidents was much lower than the EMS ops. Seems the ops with the higher operational control oversight have better luck at IIMC than those without like this flight.