Belgian,
Over here, Y/D(or D/Y, depending on which sort of supply you are after) transformers form the bulk of our Distribution system.
D/D transformers are used on really long stretches of line, as a voltage stabiliser and these are normally run through some sort of an automatic tap-changer.
Just a note about transformer earthing, regardless of where a tranny is installed, it has to be earthed by a driven earth stake, this earthing is regularly tested.
According to ECP 35 over here, the use of the Earth Potential Neutral as a common between the LV and MV sides of a transformer, is to be avoided, because of the very real risk of back-feeds. [Linked Image]