The msn dont have at the momment a sitemap like google ... :-o They scan all the content of your website that have a link ... They dont think if you have rel=nofollow ( sometimes ) or if your url have got ? or & ...
They don't have a sitemap, but you could try to get links to burried pages to see if you can get some deeper spidering.
Or you could try placing a link to a html sitemap on your website. They will follow html links just normally.