Yes there is (of course) a way to get the link category description since it is saved in the database. But you can’t do it from the template tag, you have to edit the function(s) yourself.
Under the directory wp-includes you’ll find the file bookmark-template.php with the corresponding functions. If you want to include the description in the wp_list_bookmarks-function you can use the tag $cat->description in the array loop. For example, at line 227 you could change this line:
$output .= "$title_before$catname$title_after\n\t<ul class='xoxo blogroll'>\n";
… to this line:
$output .= "$title_before$catname$title_after\n\t<p>$cat->description</p>\n\t<ul class='xoxo blogroll'>\n";
You could obviously change the formating to whatever suits you, or even build it up with dynamic “before” and “after” tags for the function if you need the flexibility.
Good luck!
