> Those 40mm PSU fans, and the PSU, are what they are replacing with a DC bus bar.
DC (power) in the DC (building) isn't anything new: the telco space has used -48V (nominal) power for decades. Do a search for (say) "NEBS DC power" and you'll get a bunch of stuff on the topic.
Lot's of chassis-based system centralized the AC-DC power supplies.
Those 40mm PSU fans, and the PSU, are what they are replacing with a DC bus bar.