How to load modal form on page load using ctools?
This post I wrote a while back deals with CTools AJAX events at any time. It involves writing your own Javascript handler and executing it on page load.

    Drupal.CTools.AJAX.refreshElements = function() {
  var url = '/mymodule/ajax/refresh-elements';

  try {
    $.ajax({
      type: "POST",
      url: url,
      data: { 'js': 1, 'ctools_ajax': 1},
      global: true,
      success: Drupal.CTools.AJAX.respond,
      error: function(xhr) {
        Drupal.CTools.AJAX.handleErrors(xhr, url);
      },
      complete: function() {
      },
      dataType: 'json'
    });
  }
  catch (err) {
    alert('An error occurred while attempting to process ' + url);
    return false;
  }

  return false;
};
$(document).ready(Drupal.CTools.AJAX.refreshElements);


Set the URL to the callback URL of your module.  The last line tells the ajax to happen on page load but this could be replaced to happen in response to the exact event you need it to.