Not sure, but suspect they'd leave lanes accessible, if needed.
Sure, I guess they could have remote controlled mines, but something like a claymore seems more likely, if the didn't do the above.
I've heard rumors of Ukrainian military movements, but not much more than that.
Supposedly, as more and more Russians pour into Crimea, tensions are growing worse, and the civilians of both sides are getting more agitated.
Of course, as Putin has said there are no Russian troops in Crimea, so perhaps they are well organized terrorists who should be shot on sight, since they are not part of any national military force which would otherwise be protected by the Geneva Convention, and the rules of war.