As far as the old cellulars remember, a throw over yoke is not legal when fitted to an aircraft being used in the initial type rating conversion. As you say, I wouldn't sit in the right in such a situation anyway. It certainly does not consitute fully functioing dual controls.
Once the trainee is type rated I would suppose that it is legal enough for advanced training, although I cannot remember whether the ANRs specify dual controls for a safety pilot.
One does actually, sitting in the right, have a pretty good control over the single yoke, especially around the lateral plane, so while the situation is not ideal, in an advanced training context it is probably not dire.
