Not only have supervised injecting sites being proven, well beyond a reasonable doubt to reduce deaths and crime in a given area. Multiple small studies in various countries have shown that HAT treatment (heroin assisted treatment) is even more successful (along side shooting galleries/needle exchanges etc.) In HAT treatment you go to a clinic, similar to a shooting gallery and are given, for FREE or at most a negligible free, pharmaceutical grade heroin, which you may then use, hang out for a while, then go on with your day.
The biggest problem with methadone and Suboxone as a treatment is a lot of people aren't ready to make the jump from heroin. When given pharmacy grade heroin for free or near free, with naloxone and a RN on site to use it, you're able to grab (almost) all those people who aren't willing to switch or quit. Pharmacy grade heroin, used with clean needles with naloxone on hand is no more dangerous, even less dangerous than multiple opioid options used daily in hospitals in the US and all around the world. (Repeated needle punctures, even with clean needles are dangerous, don't get me wrong, just dramatically better than the alternative.)
Last time I looked, maybe 6-7 years ago, I found at least 6 studies, all in different countries, the total fatality rate with HAT treatment was ZERO (until the studies stopped and dozens of people would die in the area over the next year or two.) Of course the big concern is that more people would start using heroin, but every study showed the opposite, as have studies about decriminalization, legalization, etc. (Heroin is a lot less cool and fun when you go to a clinic to use it with a RN onsite.)
There's this myth that addicts have to hit "rock bottom" before they change. For some people that may be true. For many (maybe more?) the opposite is true. Stabilize a heroin addict with free pure heroin and what are they going to do? They tend to re-engage with family, with society, with non-drug using friends, they get jobs. Not having to constantly think about when they can next score, many of these people, in the studies I read at least, started choosing to taper their dosages (on their own) with a number quitting heroin completely. And for those who don't quit, at least they're alive, not spreading diseases, committing less crime, and are more engaged with society in a positive manner.
The studies were small and like I said I only found 6, but the logic is there, and while I wouldn't bet my life on it, I'd bet a huge sum of money that large scale studies of HAT treatment would find the same, less death (dramatically,) less crime (dramatically), less spread of illness, less drug use, and a better community. The fact that needle exchanges and shooting galleries are still controversial is a f'ing crime. I first read about HAT treatment around 2005, it's nothing new. Needle exchanges and shooting galleries are even more widely proven. But hey, war's are fun, and on rare occasions there's no one to bomb or shoot so at least we can keep the drug war going! Since we must always fight the enemy! (doesn't matter who/what the enemy is, we just need to fight it!) /rant