This is because I see 3D tracking as a step up from 2D tracking and so I wanted to test my compositing workflow tracked to the Tracker node before the CameraTracker node.
In 2D tracking, you can manually pick one point that you think will track well. Then you copy the translate values to a Transform node on the trackable elements. In 3D tracking, the system picks the points. For this track I chose initially 300 tracking points. This is because the camera moves a real lot. After this, basically, you can export the camera information for rendering 3D elements to composite in 2D pipeline; composite 3D elements within Nuke; or composite 2D elements onto 'Cards' which are connected to the 'camera' in your 3D 'scene'... This give you an idea why I see 3D tracking as a progression up from 2D.
I have placed this 3D sphere into the plate:
(Bottom right)
The majority of work on this shot will consist of 2D roto cleanup and possible additions of subtle atmosphere and fog which are of 2D stock footage. So, I will see what this entails in regard to things looking correct or flat and odd.
Here is the track so far:
I am very pleased with the solve. I have achieved a low Solve Error and it looks good to the (my) eye. It follows the many movements of the camera convincingly. I am quite impressed by the Nuke workflow and output here.

