Bear in mind the OP's rack has European-standard lighting mounts, not US-standard. The difference is that the Euro lights mount with two screws 50mm apart horizontally, and the US lights use the reflector-bracket standard two holes, ¾" apart vertically.

I don't know a thing about the Blackburn light, but I've yet to see a single light that supports both US and Euro rack-mount standards.

This is why I didn't recommend the CatEye TL-LD-1100 the OP asked about. I have that light on an American rack and absolutely love it. It can't be mounted on the Tubus without a lot of zip-ties, duct-tape and assorted ugliness.