What you ask is impossible currently.
Even if you were going from the Acela train to the CubAcela in Boston or Washington, you would have to unplug, since the wireless network on the Acela is different from the one in the station. It is not like cell phones where the equipment switches you from tower to tower automatically.
Commuter railroads have been very slow to adopt wifi. Subways and Metros, to my knowledge don't have it anywhere in the US. You'll be lucky to get signal (phone or data) on a smartphone in most subways.
Try again in 10 years.