D&RGW Pile driver OB

Concerning the on-going restoration of OB, I'm looking for any information as to how it was powered. Several undated photographs show what appears to be steam pipes coming from the steam dome of a host engine and feeding into OB's steam engine through the roof of the hoist house. This makes sense. But several people have indicated that they thought compressed air was used. This would be a considerably safer method of demonstration if it would work. One has to assume that it would require a very large volume of air. I question that even a locomotives air compressor could handle it. In any case, any info regarding this would be greatly appreciated.