Those are the 3 test bed SD60MAC's that EMD built for testing of the AC systems. I think they are or were decomissioned after the testing. Steve
The SD60MAC's were on BNSF's active roster until mid-1998. They were at the Transportation Technology Center in Colorado by July 1998 and remain there today.
They laid the groundwork for the first order of AC-traction units by BN in 1994. Nice shot of all 3 SD60MACs!!!!!
I just checked and there were three in my picture: 9500, 9501, and 9502 here. The other is probably like a "control" unit to test changes?
The 9503 was delivered much later. Most of the testing was completed by that time. The units were used as demonstrators for a short time on other roads. When BN took delivery of the SD 70 MACs, they were placed in train service on the BN.