Thanks for taking the time to go over this in some detail. Very much needed information.

It does not "appear" that BART is going to solid steel wheels or tapered contour, but I could be wrong about that. As to plug doors, they are cool and appropriate to streetcars where there aren't so many doors. But on a long BART train with now more doors per car than heretofore you are sticking your neck out. Overall I think sliding doors are more functional for subways and less likely to run into issues.