Experience with drug addicted bio-parents?

Does anyone have any experience you can share with regard to drug addicted birthparents? We have had our FD since she was born. Her father was in prison on drug charges. He has had a lengthy history (about 8 years) of drug charges, among others. He was incarcerated for two years. He just got out about five months ago and, though our FD's goal was changed to adoption last summer, they are now working toward RU. We do not agree with this because of the bio-dad's long history of drugs and arrests, we feel it should take longer than a few months to prove that he is going to stay clean and out of trouble. The agency does not drug test him and since he served his maximum prison sentence, he isn't on probation. So nobody is checking to see that he's staying off drugs. They feel since he was incarcerated for two years and couldn't do drugs (at least not theoretically -- but I'm not naive enough to think that inmates don't ever get their hands on drugs), that he is clean. But I have my doubts. I thought a person had to make a conscious decision to get off drugs and seek help to truly overcome addiction -- not just be forced to go "cold turkey" by being incarcerated. It doesn't help me to know that he is involved with the same group of friends he had before he went in and that at least a fourth of his friends also have drug charges against them. They have started to send our FD on unsupervised visits with the bio-dad for a few hours at a time and it makes me worried sick while she's gone. We have retained our own attorney, but I know they are going to argue that we don't have standing to file for termination of parental rights. And it depends who you ask and what you read -- the law seems to be a gray area in my state in that regard. And, to further complicate things, we have already adopted her older sister, so moving her would mean separating the siblings.Please share your experience with the likelihood or lack thereof of overcoming an addiction while incarcerated.Thanks