I don't know if this qualifies as a stealth regen, but the observation is probably worth posting anyway as I found it interesting. I had to stop for what turned out to be a very long TRAIN. I sat with Auto-stop on for probably 10 minutes (I didn't time it) with A/C running (very hot day). As I sat, I noticed the battery charge bars very slowly slipping away...started with 4 bars...when it finally dropped to 1 bar, auto-stop disengaged (with my foot still on the brake) and the engine fired up. The interesting thing is that as soon as the engine fired up in idle, regen immediately went about about a third of the way to max and just held there (at least a full minute or so or until took off when the train cleared). So the ICE was turning the electric motor as a generator to re-charge the battery as I sat. The train finally cleared and away I went. I was back up to 4 bars after about a mile of travel and a couple of decel's and braking for 1 traffic light...probably 2 minutes after I took off from the train stop.