A 12V bus would be massive, and wildly impractical for any size of data center. I don't see much advantage of a DC bus over an AC bus at the power supply, but one thing it DOES do is eliminate the pointless DC-AC of the UPS inverter which is immediately just stepped back AC-DC. This voltage unfortunately fluctuates between 584V float and 408V at the end of battery discharge, though, so it may not be entirely practical. But, if it's just switched power supplies, the PSUs might not really care *what* the voltage is, and be just as insensitive to DC voltage as they are to AC voltage.
I do know the military makes a lot of use of 416/240 and this is apparently a choice based on wide deployment compatibility issues. Look for large military surplus gensets and you find many, if not most, are made for, or are currently wired for, 416/240 or thereabout.
416/240? Are you sure? I can't recall ever having seen one. 440V and 460V, and a slew of 400V and even some 400Hz but never 416V. 400/230V 50Hz is the standard voltage for most of the world, and just as common in the military as 208/120V 60Hz. In fact, most of the time, the generators can support any of the 3 common voltage/frequency combos with some minor tap changes to the coils (parallel or series for 480 or 208V) and a small adjustment to the controller for the specific frequency and voltage.
