I have been in this situation many times. If his attitude is awful he is not there yet…. but really that is not for you to fix. It clearly will help him if the rehab faxes the probation officer. Has he signed a release for you to talk to the rehab? If not they will not talk to you either. So I would tell him that he needs to sign a release for you to talk to the rehab otherwise there is no way you can help him. If he doesn't sign then there really is nothing you can do. If he has signed then I would call the counselor at rehab and tell them that probation wants a fax that he is there and of course they will need a release. And let them handle it (or not) with him.
When my gig has been in rehab willingly then he has usually signed releases when needed. The recent place he was at for 6 months, he signed the release allowing them to call us if he left (a requirement for him to stay there) but did not sign for more detailed info but that was ok with me. I do not need the details of his treatment.
So I would support him while he is in rehab….but if he gets nasty with you then I would tell him you are not going to talk to him and hang up. Don't put up with him treating you badly.
