hot/cold-potato routing

I'm new to the world of high-end/ISP-level routing and traffic manipulation. I recently heard of "cold-potato and hot-potato routing" and have developed an understanding of what it means and why hot-potato is default because of BGPs very nature. My question is, How is Cold-Potato routing implemented, and how are ISPs like Above Net able to just switch over when a backbone connection is lost? Are MEDs involved? Thanks, -=Vandy=-