Batch API callback method is not call
Try specifing the file where your functions are located. 

Even if those functions are in the same file as your #submit callback, the file path may be needed.

$batch = array(
  'operations' =&gt; array(),
  'finished' =&gt; 'user_delete_tickets_batch_finished',
  'title' =&gt; t('Processing delete user tickets'),
  'init_message' =&gt; t('Deleting user tickets is starting.'),
  'progress_message' =&gt; t('Processing...'),
  'error_message' =&gt; t('Deleting user tickets has encountered an error.'),
  'file' =&gt; drupal_get_path('module', 'your_module') . '/your_module.module'
);