As I have read in a comment in the blog accompanying our TUIO AS3 project, there is a software overlay that you can use on a Surface 2 tabletop system to forward the Microsoft touch and fiducial events via TUIO to TUIO-based apps.
I have not tried it so far but hopefully I will have the opportunity to test it, soon. If so, I will report here. Yesterday I had the opportunity to test Surface2TUIO on a Samsung SUR40 device. It works like a bliss. After starting it, a small window opens telling that Surface2TUIO should be working. The application simply forwards Microsoft touch events as TUIO messages. By the way: Surface applications are still working next to Surface2TUIO.
As the link to Surface2TUIO in the forum is dead, you can download it here in the meantime.