When you create a .dwf from a Civil 3D file, the C3D information goes along for the ride. If you plot the points, in Design Review switch to the selection tool and grab one of the points. In the properties you'll see all the information that you saw in C3D. Measuring distances is a little less accurate in my experience but should give a good idea of what the distance is. I wouldn't expect to measure with a precesion less the 0.1'.