This is so sad, FreeOwl. Sadly it is all too common. I've never been homeless, but I have gotten to the point of chugging a bottle to keep DTs at bay. I'd always be astonished when it was all gone... Like how did this happen?! Panic!
The system really fails people with respect to mental health and addiction issues. Many policymakers feel that it is not worth an investment as addiction is a "choice" and will eventually be a waste of funds. So backwards!! ER visits are incredibly expensive, etc. I'm sure your friend feels hopeless. I saw people trapped in similar situations when I was at rehab. One older man who was also homeless left and came back 3 times because he was literally put on the street... Then the cycle of booze again.
I think you did the right thing. Hopefully they will find a placement for him in a detox/rehab facility. He can't possibly want to continue this way. Cunning, baffling, and powerful... I hope it works out!