I'm a daily commuter to the bay area on the capitol corridor amtrak right now, coming to you via tmo 3g.
There was an amtrak rep on the train one night in Jan, and he gave me the WiFi skinny for the Capitol Corridor.
The capitol corridor train in norcal is actually run by the CCJPA out of Oakland, which made up of the connecting transit agencies like BART.
They have had their test run and chosen provider for train wifi for a while, but the bureaucrats at caltrans dis-allowed the funding for it saying that their pilot program was not caltrans approved. Yay Sacramento.
This dude confirmed that WiFi will be free
and coming to at least some of the trains around Q3 this year (however fares are going up in the spring
). He also mentioned that it was going to save some money for the system in inter-train communication that they currently have a vendor for.