I've worked for two different agencies. The first, a municipal PD, allowed me to carry whatever I wanted to. I carried a Glock 22.
My current agency does not have an open carry policy. We carry what we are issued, and we have no say in that matter. Our replacement handgun bid went out around 2 years ago and the same manufacturer landed the bid, along with basically the same gun. I now carry a S&W 4006TSW.
The only input we are allowed is for secondary (back-up) weapons. We are fairly open in that respect, as long as no smaller than 9mm / .38, and no larger than .45 / .357. Shall have the ability to fire double action, and shall have a manual safety, with the exception of Glocks.
I've carried a S&W 4006 for nearly 15 years now. While it was not my first choice, I've learned to like it and now I would gladly pick it over MANY other guns.