I did a lot of my marathon training like this last winter (I'm in the midwest). I found I had no problem on the bike paths with just a headlamp. However, super fast stuff was not the same, that's for sure. Running MP or HMP or even a little faster was not a big deal. But if I wanted to hit around 5k paces, I was just not able to stay as relaxed and hit the right times.
Fortunately my preference for training involved more long intervals and fartleks where I didn't worry about pace and just ran comfortably fast, whatever that happened to be in the cold, wet, snow, or ice.
Also, check out the tracks periodically. Lane 1 might get shoveled, you never know!