Again, it's not a compromised individual case like you described, it's an institution, HSBC, giving permission to US to dig up old records. Upper management of HSBC knows the situation. Well, yeah, an individual is harder to track but not an institution. China may not have outright jurisdiction in HK but it should have eyes, ears to find out first hand what's going on and have its own secret agents to preempt such things. They should find out who's the designated point of contact inside the bank with FBI and have him assasinated , just an example.