I believe all electric locomotives were used exclusively in the pit. Don Strack has written an extensive history, including locomotive rosters, of the Bingham Canyon Railroads here:
utahrails.net
I don't know if any motors ever ran outside of the pit or crushing complex. That was left to the B&G's steam locomotives, including a couple of mallets, as well as some D&RGW power. Look up "Desert Empire" on Youtube; an extensive portion of this 1940's D&RGW-sponsored film is devoted to Bingham Canyon, showing the pit, blasting work, the town on Copperton, and, of course, lots and lots of trains.
Which museum are you referring too? I know of four in the country that have at least two of the Kennecott motors.