I have trouble with the iPhone under two circumstances: At home and on CalTrain. Our house is made of stucco, which is a giant faraday cage. The workaround has been to install a cell booster. CalTrain is a giant metal box going 79 mi/hr - a worst case scenario for any cell phone on any carrier.
Now, I know that CalTrain just announced service reductions and parking fee increases, so maybe it's not totally apropos to talk about improving things, at least not "in this economy" (how many times in one day do you hear that phrase?). But still... They could add a two band repeater to the luggage cars as a test.
According to Wikipedia, CalTrain was considering adding WiFi service back in 2006. The problem with WiFi is that it doesn't help anyone make phone calls, and it's more expensive, since it means that CalTrain has to obtain mobile Internet access itself somehow.
A cellular repeater in a train car isn't the same thing as microcells in airplanes. There, the signal is back-hauled over satellite links since cellular phones are actually not licensed for use in the air (their widespread visibility to multiple cell sites causes interference).