There were a few Baltimore/Washington area agencies that issued semiautomatic MP-5's in lieu of the shotgun. As I recall, two were transit police forces. I did see an Ocean City Police officer with his assigned semiautomatic at an IALEFI RTC a couple of years ago. A few years prior, he would have been the coolest kid in class. As it was, he was jealous of the AR-15's the rest of us had.
We also had the semiautomatic Colt AR-15 back in the day. Given the limited training and support for that platform, I preferred the shotgun. I was somewhat perturbed that, during the Beltway sniper case. I ended up with the Colt because I was one of the few qualified with both weapons. If you have ever read the book "Sniper", there is a photograph of my patrol car on a high-risk stop of one of the "white box trucks" we stopped. I had just been directed to trade my slide gun for a big 9mm pistol. I am clearing the cab, jut out of the photograph. I still recall thinking that if the suspect suddenly popped up, I would much prefer to have my 870 in hand. Ah, good times!