"Have you found any good papers on the Highway's physics?"

Not really. The LTool is suppose to be program that charts out potential routes.

There is this:
"In current mission concepts, like for the ESA interplanetary mission BepiColombo to Mercury, ion propulsion systems
are being investigated that continuously exert a small force on the spacecraft (’low-thrust propulsion’). Thus, it is
necessary to include a low thrust control into the PCRTBP. The idea of intersecting manifolds of periodic orbits as
mentioned earlier will therefore be enhanced in order to compute suitable reachable sets [6]. As an example we present
some numerical results for an Earth-Venus transfer."
HTML

Pdf:
http://www-math.uni-paderborn.de/~agdellnitz/papers/DePaPoTh2007.pdf

Oh, I found this:
"It may thus be possible for a spacecraft to ”bridge the gap” between two pieces of trajectories in the vicinity of these manifolds by exerting an impulsive maneuver"
http://www-math.uni-paderborn.de/~agdellnitz/papers/DeJuPoTh2005_CELMEC_IV_v2.pdf

That is sort of what I was thinking about.