How can you get internet on a train?

Question

There are some rail road companies offering an internet connection to their customers. How can they do it? What kind of internet connection can they have on board a moving vehicle?

• Satellite connection? I think the train movement will displace a mounted dish and it also will have to be constantly moved around to find the satellite as the train makes turns. Speed isn't greater either.
• GSM connection - EDGE, UMTS, CSD? 3G coverage often is not an option in rural areas where train goes. These kinds of technologies doesn't offer good speed.
• WiMax? Wikipedia article on it says it could provide 40Mbps for long distances. Is that what they use mostly?
• Some kind of power line internet carrier?

Answer 1

Here in Canada, the main train service (Via Rail) uses WiMAX. You can read some details about a train WiMAX setup here

Answer 2

Here in Sweden the trains have satellite as main connection backed up with 3G and GSM. My guess is that this is the common way for all rail roads.

Source in English

Most of the time you surf via satellite and then you get most bandwidth. But so that you can surf without interruption we run a number of parallel links (both 3G and GSM). So while the train is driving, the system is always looking for the best connection.