Chromakey usage with a black-background?

Hi all,

I have a video – the one here http://www.123rf.com/footage_12750562_transition-with-petals-includes-matte.html – that is a video effect rendered on a black background. I would like to overlay this, and I am thinking that chromakey is close to what I want. But since this background is not a particular color, the settings that I have played with in both Chroma Keying Basic and Chroma Keying Pro just don’t seem to have any effect. Can anybody think of any technique that I can use to make this work?

Currently there is no Luma Keying in BoinxTV to achieve this in BoinxTV. The only solution I can think of would be replacing the black with green or with transparency in something like Final Cut or another Editing application.