If executed correctly, then jail is a actually good solution for heroin addicts. In jail, they can't leave to buy more junk, so they'll overcome withdrawals with a 100% success rate. The hard part is staying clean.

Heroin use was popular in the Beatnik generation. In the book Junky, William Burroughs describes how had himself jailed voluntarily. Police stations where he was living at the time had a program similar to Gloucester's where users would bring in their "works" in exchange for a 21-day lockup without charges.