Both S&W and GLOCK won a contract from the BATFE to supply pistols, it appears that GLOCK has been named the “Chosen Duty Weapon” of the agency. My understanding is that agents are able to chosen between the S&W M&P and GLOCK for their personal duty weapon.
From the GLOCK press release …
I am pleased to announce to you today, that along with the awarding of the contract with the ATF, GLOCK has been officially named the Chosen Duty Weapon for the agency!
This choice comes after rigorous testing and evaluation including a 20,000 round endurance shoot and brutal environmental testing. The ATF selected the GLOCK 22 Gen4 and 27 .40 caliber semi automatic pistols as their choice of duty weapon; demonstrating that GLOCK earned their trust and confidence!