dojo component in tinymce plugin

Trying to use the LegacyDialogPopup in tinyMCE but i dont get how Episerver is doing it.

Looking at epi-image-editor.js Epi is doing it like this:

define("epi-addon-tinymce/plugins/epi-image-editor/epi-image-editor", ["epi/routes","epi-addon-tinymce/tinymce-loader","epi-cms/legacy/LegacyDialogPopup","epi/i18n!epi/cms/nls/episerver.cms.tinymce.plugins.epiimageeditor"
], function (routes, tinymce, LegacyDialogPopup, pluginResources) {
    tinymce.PluginManager.add("epi-image-editor", function (editor) {
....
}
});

But when i register my plugin

.AddExternalPlugin("MyPlug", "/pathtoplug.js")

and use the same pattern as upper code:

define("myintegration/plugin/myplug-tinymce", ["epi-addon-tinymce/tinymce-loader","epi-cms/legacy/LegacyDialogPopup"
], function ( tinymce, LegacyDialogPopup) {
//this code never runs
tinymce.PluginManager.add('myplug', function (editor, url) { ... });
});

How do they register their addons to run in the dojo context?