Yeah, I get it, and that trackplan makes sense to the OP. I think my terminology fowled my idea.
To rephrase - Wire two buttons (electrical switches) at the bumpers at A & B, with wire all the way back to the turnout motor.
When the trolley hits point A, it will
1)change direction, running towards the turnout (switch)
2)Press the button (electrical switch), throwing the turnout (switch) toward route B
From there, the trolley heads towards C, running though the thrown turnout (switch) . After contacting the bumper at C, it reverses direction, and it will follow the turnout (switch) toward point B, where the opposite happens. Repeat.