Police agencies in the US are increasingly carrying Narcan. The practice is becoming more widespread. I went to the American College of Emergency Physicians conference last fall and there was a guy there who had a Narcan autoinjector designed for layperson use (family, police etc...) that talked you through use of the device. (I'm not endorsing any particular product but this was the device. One of the guys who developed it is a paramedic turned physician. The other is his mechanical engineer brother. I met the doc half of the brothers. Nice guy.)
While I can't speak for other areas places where I have worked and currently work see the police more interesting in keeping people alive than in arresting them.
It's interesting, too. I've heard the same argument about users not going to the hospital because the people there are assholes. What's funny about that is that I think the users think that everyone who's not falling over themselves to help these poor, downtrodden heroin addicts... "Because I have a DISEASE!"... is an asshole. They aren't treated any differently from other patients. But when people are working to take away your high...
(As an aside I did meet one addict who came in after shooting into her hand. She was actually pretty nice. It was a slow morning. I had no other patients. We talked for an hour. She walked me through how she buys. How she prepares the solution. How she decides where she's going to inject. It was pretty fascinating. I got a better drug education from her than I've gotten in years of lectures.)
There was a NYTimes article on supervised drug injection locations last year. I thought the article talked about a place in Washington but it was really about a place across the border in Vancouver, BC.