Unfortunately people can still have a fatal overdose on methadone though it is a lot less common to happen accidentally vs fentanyl overdosing.

I can't speak to the clinic in Burlington but clinics are usually highly restrictive especially in the beginning of treatment. You have to show up at a certain time to receive your dose everyday. If you miss it you can start to be in withdrawal. Thankfully another drug available is called Suboxone and that is something that people take on their own from home. It isn't always as effective as methadone but it's the same idea of maintenance therapy. The goal with maintenance therapy is not always to get the person drug free as in off the medication. If it is effective for them many will take it for years and decades. The unfortunate problem is these drugs don't work for everyone. If you were to just provide the pure version of the drug they already use it would have similar outcomes except a much broader benefit to society at large.