Traditional O22 style switches have this capability built in!
1) Assemble your track. The key here is to add an additional insulating pin on the center rails leaving the straight and curved paths from the switch (but not the base of the "Y").
2) Run track power (say a lockon) to the line at the base of the "Y".
3) On the switch motor, there are 3 terminals - take an end terminal form the switch machine and run it to the center rail of one of the paths leaving the switch. Then do the same for the other terminal and other path leaving the switch.
4) Wire up the O22C switch controller as normal. This can be used to control which trolley line is active.
