Hi,
I recall seeing ads for this bridge but never saw one "in person"
My thought would be to look for a once popular "Switchmaster" turnout motor.
http://www.builders-in-scale.com/bis/sm-home.html
It would probably be more adaptable with its rotary action instead of a linear action of a Tortoise swirch machine. Still, in a pinch a Tortoise could be rigged to provide the motion you need. Some folks have used them to actuate overhead doors on structures.
There are DC servos out there that some of the aircraft modelers use that you might find adaptable but I'm not sure if they would be strong enough. The Switchmaster has plenty of torque.
I presume that an actuating wire or nylon filament line could be drawn through the layout roadbed to connect the rocker to the actuator.
AHM did make a #2810 motorizing kit for this bridge but I don't know how easy it would be to track one down.
Here is some information which may help:
http://www.theweebsite.com/trains/scherzer_build.html
Good luck, Ed
I have an old AHM kit for my n scale layout of a rolling bridge. I am going to build this and install it on my layout expansion. It is operational... by hand. I have seen videos of this bridge operated electronically, and was wondering if anyone out there has done this, or could recommend a good motor or electric system for making this possible. I look forward to hearing from all of you. Cheers.