WE CONTRACTED ABB TO INSTALL A NEW HOIST CONTROLLER & SKIP LOADER PLC. DURING THEIR FINAL COMMISSIONING & PROGRAMMING PHASE A HOIST FAILURE OCCURRED, RESULTING IN THE CHUTE LOADER REMAINING IN THE OPEN POSITION. THE HOIST MAN NOR THE ABB PROGRAMMERS WERE UNABLE TO MOVE THE SKIPS MAKING HOIST INOPERABLE. WE EVACUATED.