Well, i dunno about Bretonnia, but what i read on my wiki walks about Tobaro, the closest Tilean city to Skavenblight after all, indicates that they know basically nothing about the Skaven and even their Deep Watch, which was established to watch the caverns under the city after a Skaven invasion, considers them myths and nightmares.
I think it very much depends on the source, from what I read most of Tilea and Estalia knows about the Skaven and considers them among their worst enemies for assassinating Myrmidia among many other wars and horrors.