I can't say for sure, but it can't be just any xml data, it has to be in a specific format before the SMP will use it.
I believe that XMBC uses a different format so the SMP won't use it. However, there is already a scrapper that will, THUMBGEN. Just make sure that you set it up so that will generate for the WDTV live HUB format (the HUB and SMP use the same format).
There is also a scrapper developed by a user which you can find in the HUB's forum HERE.