Special:myLanguage finds the correct page, but then looks for a subsection with the English title, which of course it fails to find. Siebrand offers this workaround:
This will work if you add anchor points to your pages that cannot be translated. For example, add to the source text to allow anchors to always work. I experimented with this a while ago. The exact implementation may differ from what I write here, but I'm certain it's close. siebrand 08:44, 23 August 2010
This is working on a number of pages, so appears to be the correct solution for us.