Hmm, it's a good idea in principle, but I'm not so sure it will work.
I don't think the average heroin user is that bothered about jacking up in a safe environment, to be honest.
No city is going to be "happy" to have one of these centres, but then these are also the people that moan about needles being found on the streets.
The idea is a good one, but it certainly won't solve the issue.
On another note, I think your thread should have come with a "graphic content" warning. That photograph wasn't exactly pleasant.