Same way as the other tags. If we detect that you're setting the special "admins" or "app_id" tags, we'll use fb instead of og. We got you covered
Generally though, the fb tags are only required (as far as we know) if you want additional administrators that aren't already part of your application. That's because we're already initializing the Facebook Javascript API with your application ID, which means that those users should have admin rights already. Hope that makes sense.. doesn't hurt to re-add the tags, but shouldn't be necessary for 'normal' administration.
Let us know if you have anything else you need to know!