Did you happen to get this this to work out? I was curious because I tried to when I modified my 00 Sable switch to allow the fogs to work in autolamp mode. I was unable to get this to work because first of all I couldn't get find the fog relay. Secondly, from what I have figured out, the GEM (or whatever it is called these days) handles many of the electrical functions. And finally, I haven't found anyone with a G4 sable who has actually done this.
Also, that page on the SHO modification mentions that the foglight switch is an independent switch. On the G4 Sable it is integrated into the headlight switch.
Also, I tried to get wiring diagrams from late model F150's that use the same style of switch, but the wires are different. On the F150's there are two wires you can jump together at the switch that will energize the fog light relay when the parking lights are on. Then all you have to do is modify the headlamp/foglight switch to pull out into the Fog position in the parking light position.
But...this didn't work on the Sable either, the wires are different and have different voltages to them. On my sable the voltages ranged from zero to 12 with several wires at 5 volts. After mapping out all of the wires and the voltages at different switch positions I finally gave up. Nothing made sense at all.