I’m not sure of the validity of any claim you might have against the Owners Corp but the first thing would be for the tenant to make a claim againnt you and for you to then pass that on to the OC.
I think if the fire was due to some negligence by the OC, then you might have a claim. If it was just one of those things, the Owners Corp are no more culpable than you are.
But rather than an informal arrangement between you and the tenant, get them to make a claim against you at Fair Trading, then whatever the outcome of that is – and you could settle this at mediation – you have a legitimate figure to claim against the OC’s insurance. There is no guarantee, however, that they will pay anything, depending on their policy.