Although mine is just 17 I do feel like I'm from the been there done that on this subject. I have not yet had any success though. I can only warn you of my failures.
When mine is home he goes back to his old ways. He sees positive thinking, good behavior as something forced on him in jail, placements, etc. So despite years of this, years of being told he's not coming home due to behavior, every time he gets home he goes back to what he wants to do. He has not developed any respect for me or any other adult. He has not changed his mind about using, he likes it and he's going to continue to do it. No rehab program will take him at this point until he decides he wants to stop using. Mine has never been home more than a couple of months before he's back in jail or hospital. He's never been clean when he comes home more than 2 weeks.
So my question to you is.. if the last time he was not locked up was in Aug when he ran from a program, what has changed now? Is he coping better with the feelings that drive him to use? I know there's no way to really know these answers, they'll say anything they think you want to hear. But what does your gut say?
Other thing I would look very seriously at before I'd even engage in debate with husband about it would be practicalities. Is there a 6 day a week rehab program in your town? I'm sure we can all agree that if the PO office is only paying for 2x a week rehab it's worthless. So if you can even find a suitable program are you willing to pay for it? How is he going to get there? Who is going to go to AA mtgs with him to be sure he doesn't run?
Basically, are you prepared for 24/7 watching him? How are you going to keep him from contacting old druggie friends? I can tell you that once he's out of jail and until that next court hearing the PO is not going to get involved with his refusal to get out of bed to go to rehab, therapist, AA or whatever. They're not going to care if he's on the phone all day with druggie friends. Ask them how many times he can sneak out in the middle of the night till they're going to come get him and throw him back in jail.
Have you found a therapist that he will accept who will take what the PO office will pay them? Does this person have a waiting list or an appointment the afternoon you take him out? How many times a week is he going to be in therapy vs how many hours a day are you hoping he's on your couch? Has he developed any new hobbies to keep him busy while he's on the couch or is he going to be declaring boredom leading him to running and drugs? Are you going to be able to go grocery shopping with him on the couch?
I'd look at ALL the practicalities first. And that has always made it a no go for me.