I don't think that pluging CoronaData to CoronaNormal node, would give any meaningful results, as the latter expects tangent space normals as input and the former provides object (world?) space normals as output and as you said, there's no way to link them to a camera. The closest thing to retroreflection effect, that i managed to achieve so far, was to add edit normals modifier to an object and manually turn all normals towards the camera. That gives good retroreflection, but totally screws shading of the object, not to mention that there's no way to link normals to a camera, nor to animate them. I think we need a shader that would use object's unaltered normals for diffuse shading, but would bend them towards a camera for specular reflection. Maybe that is possible to achieve with OSL? But then again, there's no way to use OSL in Corona if you're not on latest 3ds max...