Yes, it is possible. We have added a couple of custom fields to our user editor. What you have above looks good to me, except it is missing the place_before or place_after argument. It won’t show up in the editor without that.
On a related note, we have a custom field that we wanted at the top of the right sidebar, so we used 'place_after'=>'metadata'. But that only worked when editing existing users, not new users. Turns out the “metadata” section does not exist when creating new users, so the custom field had nowhere to go. We changed it to 'place_before'=>'email', and it worked (although not quite at the top).
Lesson… make sure the element you want your custom field before or after actually exists in all contexts.