btw there has never been a case where one of the teams playing in the Super Bowl is from the same city where the SB is being held that year, but ironically enough guess who the next three SB hosts are?
2011: Cowboys Stadium/Cowboys
2012: _Lucas Oil Stadium/Colts_
2013: _La. Superdome/Saints_
Well Palo Alto is about as far away from San Francisco as Arlington is from Dallas, so technically you could consider the '85 SB to be the one case where a team played in their home city.
This is the first time in Super Bowl history that two teams that plays their home games in enclosed stadiums will meet in the Big Game.