Campy actually made a tandem group at one time. They're quite rare.
Also, R&E Cycles in Seattle, WA, routinely reworks Campy single cranks to create tandem crossover cranksets for it's Rodriguez tandems and, yes, they look spectacular. I'd actually thought about doing the same thing for our Calfee using Campy's carbon cranks, alas... they didn't make a carbon triple at that time.
Back to the tandem being offered, the Phil Wood disc would best be left as an object d'art and not used. They were problematic, at best. There are some other comments regarding the Phil Wood discs in the archives that I've previously posted if anyone wants to go look. As for the dual rear rim brakes, back in the 70's and 80's all kinds of interesting brake configurations found there way onto tandems as folks who were new to tandems found their stopping power lacking and/or experienced rim-heat induced tire blow-offs. In hindsight, some of these configurations don't make a lot of sense now, but older tandems like this or from Osell with multiple rear rim brakes and efforts by Phil Wood to develop an early disc brake demonstrate that there was a need to come up with better brakes. The Arai drum remains one of the best solutions and just about all of the contemporary brake designs are far better than what was offered 30 - 40 years ago.