The one thing that is lubricated by the fluid is the seals in the transmission and without circulating fluid you can burn out the seals pretty quick. Not sure what gears are moving when in neutral but most planetary gears are constantly meshing and without circullating cooling fluid you could have problems also.
Recently to save fuel when approaching a stop sign or traffic light that I know I'll be stopped at for more than 30 seconds I've been shifting into neutral and shutting the engine down while approaching the stop at anywhere from 25-55 mph.
Maybe there's something I'm missing here, but... What happens when a squirrel (or child, elephant, mother-in-law, etc) unexpectedly runs across the street forcing you to brake, making you come up short of making it to the red light in EOC? Unlike restarting in Neutral in a MT, wouldn't you have to come to a complete stop, put it back in Park, restart it, put it in drive, get to the light, and shut off the engine again? Seems like a potentially dangerous situation when the person driving behind you (probably already up your butt from Hypermile driving ) has no clue you have to put it in Park and restart the engine 30 feet short of the red light. Coasting upto the light in gear seems to be a better option when including the potential costs of tranny damage or a $500 insurance deductible for getting rear-ended.
you can start an auto in neutral or park for just that reason.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
I don't do it. I wait til I stop, then kill the engine while still in drive. Once the engine has stopped spinning, I shift to neutral. When cross-lights turn yellow, I start engine, then shift to drive (this is the only part that could cause some wear), as light turns green I go. I figure a few cents of gas is a whole lot cheaper than a new transmission! I also only do this on lights that I know are particularly long.