My personal opinion is that since the officers are used to drawing and firing Glocks, it would be MUCH more logical to get Glocks in .45 ACP....muscle memory and all that ya know.
I would also question why the sheriff / department feels its necessary to go to a .45 ACP over a .40......I mean, I HIGHLY DOUBT that two subjects not being stopped had anything to do with the caliber of the round. It is much more likely that the subjects were on something (such as PCP) which made them feel 'superhuman' and less likely to feel the pain AND/OR poor shot placement by the officers who fired. I mean, in all honesty, and I say this with total respect to law enforcement as that is my chosen career field, most LEOs are NOT as proficient with their duty weapons as they should be. The vast majority go their entire career without firing their weapon in a combat situation and an equally alarming number do not practice with their duty weapons like they should.
Is it possible that some dealer somewhere gave them a better deal on a bulk order of Sig 1911s than they could have gotten on a bulk order of Glocks?? I highly doubt this, but I suppose anything is possible. All in all, if it were my department, I would have stuck with the Glocks.