[b][/b] The Union Pacific has indeed allowed foreign steam locomotives to operate on its trackage. Here is a partial list of known "foreign" steam on the UP:

1. SP 4449

2. SP&S 700

3. GW 75

4. ATSF 3751

5. SLSF 1522

6. TSRR 201( In steam, but towed by diesel )

There have been other steam moves which I have personally witnessed, but not included for the sake of simplicity.

The policy came about due to the actions by a certain big steam operator on another Class One railroad which were witnessed by an upper management person. That person later achieved high brass on the Union Pacific, and HE was the source of the steam restrictions currently enforced by the Union Pacific.. Names have been omitted purposely, and this issue had been discussed in full in a Trains Magazine article a few years back.