Currently it's possible to do:

[taxonomies]
"news/category" = "news/categories"

And the taxonomy pages will get the paths as expected. The default title, however (when no _index.md file is found) is set to News/Categories, which I suspect is not a great title.

I'm doing some simplification work in this department now, and had a failing test above, so I'll create an issue to mark that I'll change it so the title becomes the base name (e.g. Categories).