I heard from someone who knows what's going on with Ice Breaker, and apparently there is an issue with the ride not being able to run three trains without having a train load of riders sitting on the brakes in the blazing sun. I'd think there'd be an easy solution with a sunshade over the brake run, but apparently the park is looking for a better fix for that to make capacity as high as possible. Two train ops apparently aren't acceptable to the park.
They have the same issue with Mako and the third train baking guests in the sun if the station backs up.