For YVT's small cars, using contact wheels, on a very low volume, level, tourist railroad, anything with grooves for the suspension clamps would work for contact wire.

How much of the feeder mileage was stolen? That is critical, since the contact wire was probably 2/0, and well worn over the years (lots of apple juice). Even worn contact wire, without feeder support, should be adequate for the trackage beyond the South bridge approach.

IMNSHO, the overhead system in Yakima should have been "bugged". Energized at one end with 120 volt AC, quick disconnect. Monitor at the other end at a police dispatcher desk. Office test at each shift change. Disconnect test weekly or monthly. Cruised by properly decorated cars, never on a schedule.