We surely all agree by now that you can't sell an AdSense account (or give it away, for that matter).
However, if the account is owned by a company, as opposed to an individual, and if you sell the company, then it would seem reasonable to assume that the new owners of the business would also own the account. The account itself hasn't changed hands. But the company that owns it has. In this respect, the account is no different from any other business asset.
This situation doesn't seem to be explicitly covered in Google's terms and conditions. On the other hand, there's no reason that it should be. As far as Google is concerned, there is no contractual change. I can't see how Google can legally or contractually interfere with that.
Just to be clear: when I say a company, I mean an incorporated entity - a limited company, a corporation, whatever you like to call it - a separate entity from the individual who owns it.