KUKA sim and VC use the same file format, so you can open files made in KUKA sim also in VC. However, before VC had the KUKA OLP feature, the robot program would not load.
Now with VC 4.5 Premium there is KUKA OLP functionality, and when you open a file made in KUKA sim, you will also get the robot program. However, this only works with files made in KUKA sim 4.X, as the older format is no longer supported.