Did you read this article??? BART actually believes people will run out to buy these special mugs to drink their coffees and teas on the trains? They must not ride BART enough if they honestly think that. People bring in drinks of all types, in all containers. I've even seen a normal mug (open top) being brought in and then spilled everywhere. Most bring in paper cups from Starbucks or Peet's. Plenty bring in soda cans or plastic bottles. Once I saw someone pouring a pot of coffee into a Dixie cup.
If BART wants to seriously enforce the no beverage/no food policy, then by all means, suck it up, ASSIGN ONE PATROLLER IN EVERY TRAIN FOR A FEW WEEKS IN A ROW JUST TO TICKET VIOLATORS!!! People are not going to change their habits unless they pay a price and they certainly will not be changing the "cup" they drink from. If BART actually thinks they will make more money from selling these special mugs, I think they do not know their passengers well enough.
People need to just learn to either get up 10 minutes earlier and have your coffee early, or just wait until you get to your destination. There are plenty of Starbucks, Peet's, Seattle's Best around.....you really can't wait until then to get your caffeine fix? Then, eat caffeine pills on the train then!
I've personally seen coffee spilled on trains too many times-- "magic" cup or not, the coffee will spill one way or another. Please, BART, spend your time brainstorming on other ideas to improve the system!