You know, I don't see where there would be any problem if you took a regular Tekonsha brake controller (of any variety) and mounted on the trailer A frame. The only problem would be your inability to monitor and adjust from the drivers seat and the fact that the controller is not water tight.
I suspect that's exactly what Tekonsha did. Simply repackaged one of their standard controllers in a water proof housing and added an RF remote so you can monitor and adjust from the driver's seat. I imagine it would work just as good as any other Tekonsha controller. It wouldn't surprise me to find out it's a repackaged P3.
I bet if you contacted them they would tell you.