All I can add is that a woman I know was on maintenance
methadone. Her Dr. encouraged her to breastfeed after giving birth
and was told that was one of the best ways to slowly wean the baby off of the medication. The baby would still be getting a little bit through the breastmilk, but not as much as during the pregnancy. She was told that would make it more tolerable if the baby DID have withdrawal, and it would help eliminate the need for a lot of intervention from the Dr.