Wow! Since July, and over 900 views, and nobody has put their oar in the water yet? OK, I'll try.
Disclaimer - I am not familiar with the specifics of this arrangement, and am saying the following as a generality. I reserve the right to be wrong.
I believe you have a misunderstanding of the term "trackage rights". It means exactly what it says, Railroad B has the right to operate over the tracks of Railroad A between given points. Usually there is a charge for this privilege - it might be based on how many trains, how many cars, how many tons Railroad B moves between those points.
What it is NOT - usually - is a trade. It's very possible Railroad A has no need at all for operating over any part of Railroad B. it's also possible there is a return benefit not related to train miles - let's say at Metropolis Railroad A has a crappy passenger station. Railroad B may have a great station, but their line coming into Metropolis is in terrible condition. The 2 roads might work out a deal whereby Railroad B operates over Railroad A, and once there, both railroads use B's nice station.
You may be confusing this with the balancing of horsepower hours involved when diesel locomotives are pooled, where any imbalance is usually corrected by the same means it accrued, by providing one railroad's locos to the other until things are equalized.
Again, these are speaking in broad terms. There have been times when 2 railroads DO "exchange" trackage rights, using one line from X to Y, and the other's line from Y to Z. Perhaps the L&HR and EL did have something as you describe. But the mere fact that "trackage rights" are granted does not per se indicate reciprocity.