No, I was only aware of six. I admit I have not read every single thing printed about this, but have never heard of 21 docks. After your post, I see that someone else says this higher number isn't accurate.
I would be interested in seeing the list, especially the Corpus facility and any other TX ones. I know they are already operating here at the Port of Houston, in some other form.
Here's a map for you of P&O ports in North America, presumably to be included in the deal:
http://portal.pohub.com/portal/page?_pageid=169,1,169_82863&_dad=pogprtl&_schema=POGPRTL