url_for escape=>false, builder xml template?

The Rails documentation says "When called from a view, url_for returns
an HTML escaped url. If you need an unescaped url, pass :escape =>
false in the options. "

But I can't seem to get this to work, :escape => true has no effect at
all. Is this because I'm in an .atom.builder view, not an .html.erb
view, is it somehow different?

Taking the example from the docs itself:

  <%= url_for(:action => 'checkout', :anchor => 'tax&ship', :escape =>
false) %>
  # => /testing/jump/#tax&ship

Not for me. For me, with that exact call with :escape => true, I still
get:

=> ...checkout#tax%26ship

(tested with ruby-debug itself, in a view. So I know it's not some later
layer escaping it before it gets to the browser or something). Is this a
bug? Is it a bug only in atom.builder or something, or something else i
have yet to isolate? Or am I doing something wrong? Any advice?

I would love to know if you go to the bottom of this... I'm using HAML
and :escape => false definately doesn't work on url_for..