Accessing marker coordinates in camera tracker

The camera tracker / Tomato branch is a wondeful addition to Blender. However, I have a need for it to perform differently from its intended use.

I have a stationary camera and would like to track moving objects / pixels. The tracking works just fine, but I need to get the normalized xy coordinates (per frame) to *.txt file. I thought this would be an easy python task as I could find the information I need in the datablocks of the outliner. I now suspect that the data are not accessible due to not having a proper ID. But beeing quite new to python and really not knowing what I am doing I can be perfectly wrong.

I would very much appreciate any feedback from you wizards on how tho access the coordinate information I know is there, but just out of reach.