This is potentially very stringy material, and in fact has exciting consequences about direct observation.
If (h/Mcutoff) is a single power, in principle the satellite Planck will detect these types of fluctuations. If its a square law, no satellite will ever be able to see it. I like there approach, and I agree with the conclusiosn about the boundary conditions, everyone should be pleased b/c it actually sets up a falsifiable prediction.
The exact nature of what will be seen of course is beyond us, String theory and other qg methods as applicable to cosmology are to early in their development to make any sort of reliable guess about exact signatures. However the bulk oscillatory component in the CMB should (by most conservative guesstimates) exist at some scale.