I've had it plenty of times where no one is on an enemy point, so I go to cap it. It sounds that I am capping it, and up top where it shows which team owns which points starts changing, then BOOM, there is an enemy mech on the point that just rezed there. I have tried to do this myself on points that my team owns, and it never works. I think I have only seen bots do this, but not 100% sure.