The reason they went with the "One Way" design was operating simplicity - that way the track switches along the route only need simple spring-loaded points - they don't need switch stands or anything technical.
When they are going 'forward' the horsecar always bears to the right at the crossing track, and enters the Car Barn spur from the backside of the switch.
You could do the same thing with trolley cars in a loop or Figure 8 layout - simple spring loaded track switch points, and the catenary frogs (split points for the power) have ramps built in that always send the trolley pole pickup wheel in the right direction depending on whether you approach it in 'forward' or 'reverse'.
Looks simple on the surface, don't it?
--<< Bruce >>--