Karl, hardly a sensible option is it? As discussed above lets say BA did have a 777 or an mid haul A321 sitting around free, you still have the issue flying the aircraft back. Who do you think is going to do it?
It’s not like BA would have a 777 crew waiting in Almaty as they would have for the 767, and you might say they could fly the return crew out as pax and fly the a/c back, but think you will find even being pax outbound it would have an effect on their crew hours.
As for leasing can you name one case of you having ever heard of an airline leasing in an aircraft at what by the sounds of it was short notice? Even if possible you then have the same crew issues for the return not to mention the possibility of ground handling issues in Almaty.