SBB Re 460 097-9 and Re 460 037-5 pushed/pulled a set of Einheitswagen IV and IC2000 on one of the steepest and most winding standard gauge line in Europe for testing purposes. The line to Schwarzenburg is regularly used for testing new or improved trains. So with a bit of luck, you can catch new trains from Stadler, Bombardier or Siemens.