Good morning, Julie!
The Owen's System has been tested and approved by the NBA Music Committee. It is not an official BANA code but hopefully it will be in the future. It is not incorporated in the braille music lessons. (There are many things in the Music Code 2015 that are not in the music certification course...)
My suggestion is that you take a look at it and get a sense of what it entails. There will be webinars and articles about it coming up as well to give some foundational info about it. If, once you feel comfortable with the concepts, you receive a request to transcribe tablature, you can certainly use this code - with the very important step of providing your client with an accessible version of the code along with the music they requested! If they don't have the code to reference, they'll never understand what's going on.
Kathleen