How to translate _user_mail_text

Dear group

For days now I am looking for a way to translate the text strings in

http://api.drupal.org/api/function/_user_mail_text

German discussion:
http://www.drupalcenter.de/node/15396

English Discussion:
http://drupal.org/node/163165

If you look into the English discussion the only solution found is a misuse of t(). The only solution I could think of would be like done in the way the legal module did receive a patch http://drupal.org/node/79754#comment-1070367

Is there anyway I can translate this with the use of core functions only?

Would it be correct to implement a check for the i18n module into the core user module use hook_locale and just implement tt() if supported to translate the strings through the i18n module?