MQtranslate is a fork of Qtranslate so the hooks should be the same, and to get Qtranslate to Work in custom taxonomies I use this:
/**
* qtranslate custom taxonomies
*/
function qtranslate_edit_custom_taxonomies(){
$args=array(
'public' => true ,
'_builtin' => false
);
$output="object"; // or objects
$operator="and"; // 'and' or 'or'
$taxonomies = get_taxonomies($args,$output,$operator);
if ($taxonomies) {
foreach ($taxonomies as $taxonomy ) {
add_action( $taxonomy->name.'_add_form', 'qtrans_modifyTermFormFor');
add_action( $taxonomy->name.'_edit_form', 'qtrans_modifyTermFormFor');
}
}
}
add_action('admin_init', 'qtranslate_edit_custom_taxonomies');
this should work for you as well.