The idea was to supply three individual single-phase loads off a 3ph-circuit with a shared neutral, like a US multiwire circuit. I.e. 5x 2.5mm2 from the panel to a junction box and 3 3x2.5 wires to individual Schuko sockets.
From what I've gathered this wouldn'T be legal at all. In the case described above the junction box would be classified as a subpanel and would be required to have a main switch and individual breakers for each 1ph circuit. This is what I heard from some German sparkies @de.sci.ing.elektrotechnik.
I wouldn't like to to this at all because of the likelihood of a broken neutral in the branch circuit wiring, resulting in 220V loads being paralleled on 380V. Looks pretty ugly.
