Import translation file only for specific core module
Nope, you cannot. 

Translations are stored per project, not per module, and core is one project. Of course there is experimental Contact project on Drupal.org, but it's translation stays pretty empty as it's not needed.

Worse, in exported files (at least in my language) there is no metadata, no comments about modules these strings originated. So manually cutting this file to your needs would be pretty hard, too.