The Red and Blue Teams is a smart technique. The thing is that I have never seen implementing it, I suspect that it is time-consuming and its adoption may actually be pushed back by the senior management.
I wonder if M&A consultants/The Board of the Buyer Company/Shareholders may not have tried to avail of a psychologist to help with hubris. HRM may have some degree of knowledge of psychology, but not necessarily enough (a number of HRMs have a labor law background) to influence behaviours/mindsets of those executives pushing in favour of the deal.