Here in vienna TT was very common untl very recently. Only with the 1998 ETV changes TN-C-S was introduced as a mandatory grounding system. Where older houses were upgraded grounding was usually done via water pipe until 01/01/01 (great date, isn't it?), especially if only single apartments were upgraded without changing the main service. I've seen (and installed) systems with individual ground wires from the water pipe to single outlets. Eg. a standard kitchen (bit shoddy wiring): ungrounded outlet next to the door. Ground wires from water pipe to two receptacles, feeding 2 more. That was all. No RCD, no ELCB, nothing. 10A Edison base breakers, two of which never tripped, maybe due to previous shorts that had damaged them (some sparkies had a method of hitting those breakers with a hammer in order to reset them, the next short/overload was usually terminal). Usually kitchen sockets were (and often still are, old wiring isn't upgraded too often) the only grounded sockets around. When I renovated said kitchen i took the ground wire to a junction box and weired everything else. When I rewired the whole run all the way from the fuse box a few years later that setup had to go. Now the water mains is plastic anyway. Still I suppose at least one apartment has some sockets grounded to the useless water pipe. Removed 2 of these myself, but I guess the ground connections wouldn't have helped much anyway (the entire copper pipe was totally corroded). One was disconnected at all when the plumber installed the "new" gas water heater some 20 years ago. Just cut the wire and left it hanging in mid-air.
ELCBs were sometimes used but pretty rare. The few I've seen were absolutely huge beasts, usually mounted on the wall besides the panel, or inside a panel like the one shown in the Diazed panel thread.
