It’s an interesting situation.
But consider if the OC’s common property failure caused damage to an adjoining (private) property. The OC would be liable for that.
And the OC’s insurance policy should have a Liability to Others section that covers such property damage. Ours certainly does – I just checked it.
I can’t see that lot private property could be different to external private property.
The question might be who pays the OC’s insurance excess?