Traditional wisdom in the addiction treatment community has always held that recovery demands abstinence from all addictive substances (with the exception, inexplicably, of nicotine). Many would argue that maintenance on methadone or buprenorphine (MAT) does not constitute recovery anyway, but then recent studies of cast doubt on the efficacy of abstinence based recovery anyway. Regardless, aided by pressure from DEA, many buprenorphine providers have rigidly enforced abstinence for marijuana in their patients. A new study seems to cast doubt on that position, adding to the mounting evidence against classification of marijuana in Schedule 1.
In my opinion continuation of buprenorphine maintenance should take priority over abstinence from other substances unless use of those substances causes problems on a case by case basis.