Again, this is part of why we haven't come with a concrete recommendation on the best way for it to be done. It's because there may be jurisdictional logistics that determine that. In some areas, you may have psychiatrists available who could physically go to the patient, or you may have psychiatrists in some areas who aren't able to physically go.
In Ontario, for example, we have review board panels for capacity assessments that have been challenged. Those panels will be under provincial jurisdiction, rather than a local responsibility.
To answer your question, it might be a different mechanism in different places, depending on resources and needs.