i did the Urban Cross opener yesterday in Palos Verdes (so cal), and there was a guy in the Elite A men's race on a fixed gear. It was damn cool and I think he finished second! he'd unclip one foot before the barriers then do a couple revolutions with one leg and unclip/hop off. it was pretty impressive indeed.
mostly dirt, cross country running trail. actually a great course with a steep hill run in the middle and mostly rolling nice dirt trail. couple tight soft turns and fun downhill sections(thank god). race #4 is at the same place but i have a hunch they'll run it in reverse.