You'd be hard pressed to find a major department--in fact I don't think there is a single major metro division in the US--allowing a 1911, or any single action handgun for street use. Almost none of them--again, I can't find one--allow thumb safeties. Just about every large department I know of is striker fired only (ie Glock, with a smattering of M&Ps and the rare XD), and if they sway from this, are Double Action Only in Sig or S&W. Last I checked in with an LAPD friend, they were allowed to use Beretta 92s, and while I wasn't specific about the configuration I wouldn't be surprised if they were DAO or at least had a decocker (ie no 92G).
I am sure that within a few minutes of this post, someone will trot out a department as an exception, and that isn't the point here. The vast majority of departments, and especially large, working agencies, eschew thumb safeties and single action firearms.
Frankly, the 1911 is a significant challenge to a law enforcement agency. They are finicky when deployed across an agency in numbers... remember: everyone gets them, takes them home, abuses them, etc. and not every officer is a gun nut that rubs their pistol with a diaper. Their action requires significant amounts of training to be deployed under stress relative to the draw-and-fire action allowed by DA/SA, DAO and pre-cocked strikers. Next, they are heavy for what they bring to the table in terms of capacity, etc.
The single action trigger, much less something as light as a 1911 trigger can be, is a dicey thing in a LE setting. There are already quite a few instances of accidental / negligent discharges, of officers sweeping or covering a suspect with a finger on the trigger, etc., where the light single action is even more of a liability than other mechanical methods.
