Got a call to bail out a local (read "young") electrician in Alexandria (VA) last Friday. He had come upon a set of what we call "Old Code 3 ways". I think half of old (~50yrs) Alexandria is wired this way. We experienced (read "old") electricians have seen it many times. I learned it from an even more experienced (read "older") electrician I did my apprenticeship under. It's been illegal for 40+ years now but there's still a lot in existance. Wondering if other parts of the country have this also. Bring a constant hot/neutral to the first S3. Run a 3 cond to the second S3. (Then run a 2 cond to power the receps after the second S3) In the first box join the 2 hots and jump to a traveler screw. Join the 2 neutrals and jump to the second traveler. Put the red on the Common. In the second S3 also join the hot and feed thru hot and jump to a traveler. Same with the neutrals. At this point send a 2 cond to the bulb and put one wire on this common termimal and attach the other to the red (which is the other common). Polarity and color are irrelevant since we're gonna flip flop them anyway. It works by sending 1 of 4 configurations to the bulb, (hot/neut, hot/hot, neut/neut, neut/hot) 3 of which are illegal but it was used extensively back in the day. Worst part is that the house was completely finished and there was no way in h*** the homeowner was gonna let him cut any walls to fix it. Well fortunatly it wasn't my job so I drew him a diagram, filled him in on the legalities/liabilities and left. You guys run into this system much? (I have a PDF of the diagram I drew if anybody wants it but for all the tea in China I could not figure how to attach it to this post ... email me, I'll send it if you want it)
There are several other ways to do 3 ways including the infamous way that you only need 2 wires for the traveler leg but that one ends up with 120v on the lamp shell and tab half the time when the lamp is off. I may have that spinning on a hard drive somewhere but I hate to post it because someone will see it and do it.
As far as I can tell that's exactly what's been described in the original post - the "California 3-way" or "Thunder and lightning 3-way" as it's called in Germany. If you ground to the neutral you could hook up a 3-way switch and a grounded receptacle to a 2-wire w/o ground... commonly done in Germany pre-WWII. Grounding to the neutral was legal until 73, in Eastern Germany 90.