"I would expect the insurance company to sort out just who was to carry the can and pay out. It will be substantial. I doubt this will be a 'knock for knock' settlement."
The insurers of both BA and Miami airport, (and the ground handling team on the tug!) will be taking a keen interest in this incident but each will have to bear a substantial 'excess' or 'deductible' on their respective policies as standard practice and it is quite possible the cost of this incident will fall within the deductible, it will come down to whose fault it was and that is when the lawyers take over!
I always found the old parking system at the international terminal in Sydney was difficult, as one had to look both forwards and sideways, fortunately it was changed.