This morning I got a chance to refresh my memory, as I had an outdoor pool literally all to myself. It's not exactly a 90º turn, more like 120º, but you do turn a corner using this method. I swam rectangles around this pool and practiced both directions, so it does work. The main thing is to rotate back onto your front at the same time that you're spearing the recovering arm into the water.
In any case, there are many other ways to swim corners around the base of a rectangle, if you find yourself with this lane swimming arrangement again.
Just Google "open water buoy turns" for numerous suggestions.
e.t.a.: here's a description of the turn that I was describing, it's called a corkscrew turn: