A couple weeks ago, John Mueller of Google hinted subdomain support is coming to the Google Webmaster Tools Change of Address tool, well, today is that day.
Menashe Avramov first noticed the change of documentation about the change of address tool adding "or subdomain" throughout the documentation.
Again, if you had a subdomain and you wanted to tell Google that the subdomain moved to a new domain or new subdomain, there was no way to do that with the change of address tool. Now there is.
Here are the markup changes in the documentation from Menashe:
Forum discussion at Google+.