Re safe working - I don't claim to be an expert in interpreting work rules (even though I have taken the fireman and engineer classes). Sony was running 315 and he explained the close following this way: both trains were classified as work extras and were permitted to be closer together than regular trains, since 463 was pulling the "chase train" carrying the riders, and 315 was the object of the chase, where 463's train would deposit the riders for photo runbys. Since the two trains were coordinating their operations for runbys they were at times closer together than would ordinarily be the case. Most runbys with a chase train would involve the chase train dropping of the riders at the arranged photo location, both trains would back up and come past the photo line, then both trains would again back up sufficiently to pick up the riders before continuing on. I hope that this explanation clarifies this arrangement.
Incidentally, this might be a place to re-tell the runby story Irving Ewen, one of my friends from Portland, Oregon, told me. He was in Germany and joined one of the very early fan trips when photo runbys were a novel concept. The steam hauled special train stopped at a photo location in open country, the passengers got off, the train backed up and came forward with lots of steam and smoke, and continue on, leaving the passengers to walk to the next station and take a local train to the special's destination. I understand that this was a one-time event that caused a major stir in Germany, was not repeated on future excursions.