Think we are getting to the point of needing to know the design implementation details to figure out how well it may work in different scenarios.
If it's using just the isolated outside rail, how did they do that? If it's the whole rail on each piece, accomplished by using a non-metallic pin on the ends, that could be the simplest and might sort of have the trailing effect since the track won't go dark until the last set of wheels leave it.
If it's not the whole rail, did they just make a cut a short distance in on each end to isolate one rail?
For anything more complicated than a simple loop/oval the implementation is important since flipping the curve orientation would involve switching which rail is isolated. (like an "S" curve).
Would have been neat to see it, but MA is a bit far for me for a train meet.
-Dave