The 3985 steam locomotive has pulled modern freight twice that I remember. Once was a string of auto carrier racks as a part of a publicity campaign. Regarding the container train, the story I heard is that they needed to move the cars from Cheyenne to North Platte, but didn't have diesels available. The 3985 was fired up and enlisted to do the job.
Union Pacific has used its classic fleet to pull freight at other times. I recall their EMD E-units pulling a container train a few months ago. Their #6936 EMD DDA40X locomotive has pulled a lot of freight and just did so a few weeks ago.

Commercial aircraft flown in: B712 B722 B732 B734 B737 B738 B741 B742 B744 B752 B753 B762 B772 A310 A318 A319 A320 A321 DC91 DC93 DC94 DC1030 DC1040 F100 MD82 MD83 A223 CR2 CR7 E175