A quick google search says it's only on the STi and through years '05 to '07.
Yeah I think that is the "imma gonna double park right here bitches" switch.LOL, my younger kid (14, nearly 15) will be driving our Outback, and I took her out to drive, the other night. I decided to explain that button on the top of the steering column that links the headlights to the ignition switch, so she didn't accidentally hit it and run down her battery, when turning the car off for the night. Quirky Subaru thing, indeed.