AMOS translation UI at http://lang.moodle.org now integrates Google translator services. When translating a string, you can use this one-click feature to get the translation offered by Google. Do not forget to carefully review their translation - at least the {$a} placeholder syntax and some HTML tags are broken in the Google's translation and must be fixed manually.
Why not, before sending the string to Google, replace the {$a} bits with something else (e.g. distinctive personal names that Google will not attempt to translate) and then do the reverse replacement on whatever you get back from Google?