I commuted from near Berkeley to San Francisco for 5 days recently using their BART train. It was a lot like the experience described in this article, even though it was on the other coast.

I never had trouble getting a seat, both at the stations and at the train, so it was easy to take out my laptop. Large portions are above ground, so tethering worked for internet.

It does feel really good to get stuff done on your commute! I guess situations where it is possible pop up in many places.