I don't believe that I would find previously used or surplus equipment to be in the high-risk category. Actually, it's normally a lower risk because it is a proven solution. Spare parts, maintenance procedures, and all those things are already in place and don't have to be developed.
Most of our high-risk projects involve development of technology that doesn't exist, and that drives costs, schedules, operational risk. Also, we would add a significant contingency to cover a developmental project.