We've been moving nuclear materials for a long time, whether they be fuels, medical materials, waste, or the weapons grade flavor. Nuclear material transportation is pretty well thought out and executed. You would not believe what goes into moving the weapons grade stuff. A small (and well equipped) army would have trouble getting their hands on one of those shipments (yes, this is beside the point as we are talking about waste materials..).
On a personal level I am more concerned that the "out of sight, out of mind" mentality often associated with burying it all away will prevent us from being able to better process our existing wastes into a more stable and safe form.
Move them by rail.
Fewer movements, safer routings.