Would it be the first time hackers got something to work that a company's developers said couldn't? This is from the BBC article.To answer your question, could they? They probably could, but why would they?
Yes but they don't boot Windows from the factory. Would Apple allow a reseller to sell Macs with Windows already installed? It was hackers that discovered the ability for a Mac to run Windows not Apple, but they took a negative and turned it into a positive for them.
A manufacturer can do what they want with Android, see Amazon and Nokia. Google has contracted Asus to build its line of Nexus tablets. Them building a tablet that runs Android and Windows is potentially a conflict of interest.