I didn't see the fight you are referencing, but I can answer your question by explaining what a switch is.
The move is a reversal used in amatuer wrestling for a competitor in the base (bottom) position to "reverse" his opponent and gain the top position. In BJJ or MMA the top fighter would already have the back of the bottom fighter - whether they are kneeling, standing, or on their hands and knees.
When properly executed, a switch requires the practitioner to force his hips away from his opponent and excercise hand control while putting tremendous strain on the opponents arm - the shoulder and elbow are heavily affected.
It is a very effective counter and hard to stop or reverse when done correctly.
The main counter to a switch is a reswitch where the man being switched senses the move and immediately positions his own switch and starts the move while he is in the process of being switched. Strong hand control is the best way to counter being reswitched.
The disadvantage of using a switch in MMA is that it means you have given your back to your opponent which is very dangerous, but if practiced properly it appears that a switch could be very effective in MMA because not many people would be able to counter being that they'd be unfamiliar with it.
I've watched many MMA matches where I've scratched my head thinking that an effective switch could have made a huge difference - possibly leading to ending a fight.