The answer is "it depends". If you work for the lab, the answer is "not very" (I know of 2 or 3 full time remote workers, and they're all in the IT department and completely indispensable). If you form a contracting company that jumps through the pile of legal and bureaucratic nonsense in order to be appropriately incorporated, the answer is "we don't care where you work", though getting hired is a pain.

So, mostly, no. On the other hand, there are a number of national labs spread around the country (http://www.energy.gov/about-national-labs), and the rules may differ depending on the main kinds of work done at each of those facilities, I'm not entirely certain.

We do have a fairly liberal "work from home when you want" policy, and a formal work from home agreement can happen (a coworker works from home every monday).