Where is the logic located which determines the tpl file for the front page?
please review in /includes/theme.inc near to the line if (drupal_is_front_page()) {...

if (drupal_is_front_page()) {
    $suggestions[] = 'custom-page-front-name-here';
  }


I changed the $suggestions[] value, and I saw that .tpl.php name to the front page can be customized.

According the comment of nmc, 


  this file/code should not be modified as it is part of Drupal core


. this is only to locate where can be stablished the value.