The diesel locomotives provide help on every excursion they are part of. In several cases I know about the train would have stalled on a mountain without help from the diesel assist. In the cab of the steam locomotive there is a box with a throttle selector that controls the diesel locomotive's throttle. The 844 and others have run without diesel assist when the train was light and easily pulled.

Please don't post you ridicules rants here again until you work on a railroad or pay for the operating costs of all the steam locomotives you want to photograph.