These boxes not only need to be deeper but also have a rabbet run around the front (about 1cm deep) to accept the extra-flush devices. Without the rabbet the switch will protrude from the wall, exposing a black plastic side instead of the brushed aluminum designed to be visible.
Where there's new exposed concrete work, usually all conduits and boxes are set into the forms before the concrete is poured, so no trenching. In this case the electrician missed this though and put regular round 58mm boxes in the forms... and we're talking a big building here... Austria's fanciest "museum" of modern art (stuff like holograms and whatever, really high techy).
Some architects also started forcing electricians to use Italian rectangular boxes in Austria a few years ago, so I guess we'll end up with quite a lot of different box types here (an Italian 3 module box is pretty much the same size as a US single gang box, I think using metric screws a US duplex receptacle or switch would fit).
On top of this you might encounter old 2 and 3 gang boxes that were smaller than new ones... namely shorter. You can fit a new double gang switch to an old box, but I don't think there's a way to cram a 3 gang into an old box. I think it's about 5cm shorter.
