There are two methods via train depending on the usual BS... either;
a) passenger terminal; or,
b) freight terminal.

Option a). is cheaper, doesn't involve any crate - bike with empty fuel tank! (maybe 1L petrol remaining is okay, or else one has to demonstrate that the tank is bone dry or worse) gets rolled onto the freight carriage attached to a passenger train. Possible though may also be unlikely that the bike will travel on the same train as the rider/pillion etc.
Option b). is more expensive, bike might be crated but bike doesn't travel with a passenger train (generally) though can depend on circumstances etc.

The main issue is that there's no consistency, as has been discussed in the various threads on the topic of shipping bikes in the mainland... additionally, while the costs are low compared to freighting by truck, the risks are often higher.

YMMV