@@therocinante3443 Well, friend. Now you know. There will be more tunnels during 4014's trip to California, and during the return trip to Cheyenne. If you found the tunnel, the locations where the tunnels are (including the Hermosa tunnel) were the great places to catch 4014 closing her stack hoods. if you're in the side where Big Boy enters the tunnel, 4014's hoods are closed, and if you're on the other side, once 4014 came out, the hoods will open again.
That was never it, PTC is the real reason. 4014 now has PTC installed & certified. You may still see a diesel occasionally though as having the dynamic braking and the peace of mind of a backup is still beneficial.
