Closer to 400 volts between phases.

That makes sense. I've never learned the maths on this, but sort of understand.

Many stoves and instantaneous water heaters here run on 1 ph. 400v. So it would appear that as long as you have 3 ph. going into the building, then it's easy enough to run two wires to the local box and get your 400v. As I said, most older buildings don't have this option, so either there's only one phase running into the building, or the construction electricians didn't foresee the usefulness (or they did, but saw $$$ in the future by not doing it then!). In 1965 there were no blow dryers or microwave ovens, and in our flat there's not even central hot water to the kitchen! There was a stupid useless little 5 liter pressureless boiler under the sink when we moved in.. I fixed that by running copper pipe from the bathroom, but I'm not sure that was even legal... Well, Germans lived pretty low to the ground in those days compared to the suburban house I grew up in in Ohio, but at least our houses and buildings don't burn down easily!

My shop troubles aside, I live in a 1965 five story apartment building where juice is also tight. I've got 4 16a/230v breakers to run my 1000 sq.ft. flat. When I gut renovated the kitchen (where the power comes into the unit), I had to be somewhat creative about how to partition things so that no breaker was overloaded. The box and meter are across the common hallway, so running additional wires/circuits is cost prohibitive. We don't typically have metal conduit in this kind of housing. The wiring is just tacked up to the base layer, and plastered over. It's pretty primitive, but we mostly get away with it. Since it's 230v, no wire has to carry the amps that North American wires do.