I have to buy my own, which gives me lots of freedom to choose but also creates a situation where there is no consistancy in what's being carried either in a given area or even a given dept. For example, the local Sheriff's Office issues Glock 21's to full time deputys that want them but they can provide their own weapon if approved. So, you see deputys armed with Glock 21's, 1911's, Beretta 92's and PX4's, Rugers, 9mm's, .40's, .45's, even the occassional .357mag. The local PD's are all so small that all of their officers provide their own weapons, so again, you have a wide array of guns and calibers. The only depts you see in this area that are all armed the same are the state agencies - Troopers, Game Warden's, Marine Patrol. But even they each issue a different weapon and caliber.
Sooooo.... As an officer, I like the freedom to pick and choose. From the departmental management perspective, one gun and caliber for everyone, or very tight approval lists, make sense for consistency and commonality. IMO, if the dept is large enough and can afford to provide weapons, it makes sense for them to do so. For small depts in rural areas, finances often dictate a more creative approach and officers providing their own guns is much easier to handle, as in my case. I provide my weapons, they reimburse me for duty and training ammo.