Lets say there was 2 trainers. T1 and T2
T1 sent out Ninetales!
T2 sent out FOrretress!
T1 Predicted a switch so he decided to switch
T2 didn't think T1 would switch, so he decided to send out his Arena trap Dugtrio.
I have been thinking of using this strategy but i didn't know who would switch out first because if T2 switched out first then Ninetales couldn't switch.