"If it's true that in doing so I have forfeited ownership of those stocks at what point is the CGT event triggered?"
No, you are still the beneficial owner. Not unlike owning a property with a registered mortgage. You simply confer some rights to the lender in case you breach covenants.
Having said that, this is a messy situation and I well understand why people in your situation would feel aggrieved. This could well end up in court.
