I just got off the phone with a Milwaukee Police officer and yes, they do get drug tested.They are tested before they leave the academy and again randomly. A select number of officers are randomly tested. The officer I spoke with has been tested about 6 times.
They also are tested after any type of incident. For example an accident or shooting. So you may want to walk back your comments a bit.
I will search the Milw. Police Dept. website for a link for you about the random testing. It does state on their site that a drug test is a condition for employment.
http://city.milwaukee.gov/jobs/PO#.VM17INLQWSo
Random is not the norm...BTW, nothing in the link you provided talks about random, only a pre-employment test.
BTW, there are multiple articles where the Milwaukee Police union themselves are against random testing.