Hey guys, thought I would jump in and give some American perspective.
3-phase is totally unheard of in residential settings on this side of the pond. The highest voltage encountered here in a house is 240 volts phase to phase, for major apliances like a range, dryer, and air conditioner, as well as in multiwire circuits.
The parallel I can draw to your 415Y/240 system in a house would be our 480Y/277 system here. To have that in a house would be completely nuts, IMHO!! Just check out the Violation photos to see the hack work done on residential single phase systems. I can just imagine some of the DIY nightmares that would be created with 480 3-ph in a residence. Not to mention the danger.
By the way, the NEC requires dividers in the switch box between adjacent 277 volt switches that are on different phases.
