I can't speak for the MediaPortal guys, but on the Moving Pictures project, I spent a lot of time looking into the XBMC scraper system before we implemented our own generic Cornerstone Scraper Engine. I have not looked too closely at the new ScraperXML project (although I did take a peek and by the way it is written in Visual Basic, not C#). But if it works similar to or is based on the older C++ scraper engine for XBMC it has a couple problems.
Thank you for providing some deeper analysis on the scarper project (I myself haven't just had any free time to do so. Also my knowledge is pretty limited on the problem domain, maybe because I have always hated the XML, HTML and their nasty friends ).
I would really like to see some common project between all (free) HTPC applications that could be used for the data pulling, but unfortunately at least based on fforde's comments ScraperXML looks much too limited to the MediaPortal II usage. So, maybe MPII will contain the GPL data provider engine from Moving Pictures. Who knows, as its relatively easy to change the used providers...