Mine is speculation based upon the facilities at Salman Pak.
I think you’re believing this because you want to believe it. But from just because it looks like a duck and quacks like a duck, in this case, doesn’t make it a duck. Military officials believe the use of the airplane and training grounds at Salman Pak were for counter-insurgency training. I’ve never read anything saying that the London and Spain bombers trained there. I’m sure there are training facilities in countless other countries with a 707 and railcar. Who wouldn’t train their soldiers in such an environment?
It’s a coincidence, not a connection.