The US Dept defence tried something like this. See
http://en.wikipedia.org/wiki/Project_IcewormIt didnt work, as far as I can see because the ice moves and cuts the tunnels. Interesting though. That link should enable you to find other online references to this.
doesnt take too much times thought to come up with another idea other than tunneling in the ice. What about inflatable tubes made out of flexible but highly strong material that you flood with warm air right before you use it (you know instead of keeping it warm all the time which would get expensive).
Basically what im getting at is that government is not very creative and a bunch of determined and moderately wealthy sovereigns would be a different matter entirely.