In order to track analytics for form submissions where the form is iFramed from an external website, the following code needs to be added to the page with the iframe, and another script (below) must be added to the form itself.

[uq-widget:analytics_form_iframe form="form source url" label="action label"]

Form
The url of the source form.
Label
The label for the event to be tracked in Google Analytics when the action is triggered. e.g. 'Form submitted'

On the source form page

The parent/origin page requires the following code be added:

try {
  parent.postMessage('formSubmit', 'https://form.destination.location');
} catch(e) {
  // Something went wrong...
  window.console && window.console.log(e);
}

Example:

[uq-widget:analytics_form_iframe form="https://form.source.location" label="Form submitted"]