"You just create a new Facebook at Work account to connect with coworkers. This account is separate from your personal Facebook but works in similar ways." (https://work.fb.com)
They absolutely will not mix personal and work Facebooks.
Plenty of companies have blocked [www|m].facebook.com at the firewall, for reasons of productivity and data protection. Facebook-the-company will not jeopardise the chances of adoption of this product by doing anything that will make work.facebook.com fall foul of a similar fate.
Pity they didn't just call it Workbook, then we wouldn't have had all this confusion. Or Workface :)