Operators have to assess obstacles for engine out take-off performance. Whether they do it themselves or have a contractor do it is up to them. Where I work it is done by our performance department. Given that this already happens, it is not a stretch to expect them to do something similar for DA/MDA assessments if they wish to comply with the FAA notice. We just add 50', but I see no reason to poo poo the idea that other companies might do the homework necessary to use an MDA as a DA if they decide it is worth it.