Hepatitus C and heroine, cocaine relapse?

My husband and I are Hep C positive.  My husband is a heroine addict. He is bi-polar and is finally being treated for it.  He is currently in prison for four months due to his last relapse.  Bi-polar consists of extreme emotional highs and lows. When he gets down, he resorts to self medication.  He then shop-lifts to get more drugs.  This was his first(but very bad) relapse after being clean for a year and a half.  He is being released on the 11th of August to return home to me , his pregnant wife.  
    I am concerned of future relapse and how treatment will effect him.  He seems to be his old self again, however I read that people at risk for relapse can be put on the methadone program.  When I enquired about the methadone before I was told he would have to have the heroine in his system still.
   How does methadone effect you?  Is it like you just used heroine?