Impossible to answer your question, but I've never asked my employees to pay any compensation to customers from their pocket. Such compensations are calculated in the risk of running a business and remain the cost of the business owner.
And even if, in my country labour law strictly limits employee's liability for unintended mistake. I assume that in the UK it's similar. So even if BA would ask the ramp agent to participate in the cost of that delay I believe the costs of the fuel only (yes, we were refueled) would already exceed his liability.