This is of much interest for me. I have VP15 Suite already. I see Motion Tracking as a new feature and touted as being "professional". Yet, I have not seen one video tutorial yet where text or image is motion tracked to an object.
Yes, it it possible to track text (but not (yet???) an image/video) in VP16. You need to use latest build 261 which was released today and which offers a script to apply text to a track.
The script to add text to the track offers to use x/y-offsets. Also that added text is simply a Titles&Text Event added into a new track. So you could further offset the text in various ways.
Btw. — there is a nice tutorial for motion tracking with VP16 on vegascreativesoftware.com.