I heard otherwise. There was another discussion about this like putting your adsense ads on myspace pages, which makes a page have 2 id's, and the person had asked G about it, they said that you are allowed as long as you get permission and let G know about it. Sorry i don't remember where this thread was...to be safe just ask them!
As long as I know no two Pub-id's can co-exisits within a single page and this is a strict "NO NO" from google.