I know a local SWAT member who is also their shooting instructor. He works out at the same gym I do, and we BS between sets a lot. He said that they used to issue HK USPs to both the swat team and the regular officers as well. They eventually were forced to switch brands because they could never get parts for their USPs.
He said they still carry a few MP5s, but whomever controls the money won't ever buy any issue handguns for HK again. He said he liked them, and other officers both swat and regular still like them, but the parts issue was just too big of a problem to work around.