Ignoring the practical part of this, which is that the Museum isn't going to let you close enough to the bust to do this. But assuming they did for a second -
> with a result that rivals the scan
The linked scan contains nearly 6.5 million tesselated polygons, and surface color data in Ptex format. You are not going to be able to get within cooee of that. Any hand measured copy is going to qualify as an artists interpretation and would not violate copyright I should think.
Say you take a lot of photographs of an object, and they are stipulated to be creative. Then you can use photogrammetry to derive a 3D model. So if the direct antecedent of your work was creative, how can your model be noncreative?
Photogrammetry generally disregards essential components of what makes a photograph a creative work.