Henry,
Firstly, Define huge? We have both multiple UPS's and generators on supplies A and B. We are fed at 11kV into a private ring main unit and off to separate 11kV to 400V trasnsformers, which feed dual 4000 amp switchgear and off into wraparound bypass, static ties switches etc. and through moderate sized UPS's (550kVA x 4 per side, A & B, 480v DC battery strings). That's one of my own sites, fairly small and simple setup. Customers we have who own other places are fed at 33kV and higher, with sites capacities of up to 30mVA and above. See Dropbox - Error
The problem with having UPS's and generators, ACB changeover switchgear and the like is that it creates multiple single points of failure on each path and, no mattter how good the design is, it's very difficult to guarantee both feeds right down to the dual 32amp commando in each rack, stay on.
Now most clients have dual fed equipment with multiple supplies and A&B feeds into each cabinet, but many still buy servers with a single power supply and some network equipment, even high end stuff sometimes is single fed on the AC side. Some kit is DC @ 48V, so we have many rectifiers and battery banks to cope with that stuff. The usual solution to get around this is something of this ilk: APC, a flagship brand of Schneider Electric - APC USA - They do the job well enough, but rarely have enough ports to power a whole rack, which means you end up having lots of them....
Chagrin, I've encountered these packaged energy management chips before, although not the exact ones you've listed - I'll have a look and do some digging - they definitely look interesting, for sure.. 
I've found a company in India who manufactures a 32amp Thyristor which would be capable of switching full load in a partial cycle, awaiting some feedback now, but paralleling up a couple of those puppies would certainly do the trick as well, at a low cost.
Just a note regarding phasing, we'd never normally feed a cabinet from different phases unless on a 3 phase commando socket (a lot of the newer blade stuff and storage arrays require three phase). Doing so in a single phase rack would expose the equipment and more importantly, the people working in the rack to 400 Volts potential between the two supplies. I've seen a few places where this has been blatantly disregarded, with disastrous consequences.
Lee