Couldn't they try a PLC connection as well?

No doubt it will get priced so highly its hardly worth bothering with.

Why don't they just make it ludicrously cheap (eg £2 per journey/ or in with the ticket) and block all incoming ports (unless 'related' or 'existing') and only allow outgoing ports 80, 443 with a local DNS?

At present a lot of these public wifi hotspots have port 53 open anywhere to allow use of a public dns server - but this means you can just tunnel an SSH session over it without having to pay for the connnection! This is silly!

...for Lufthansa's trans-Atlantic in-air WiFi, which was tragically ended in 2006. It was not perfect, but made being stuck in economy class for 10 hours a little less painful, which was worth the extra ticket cost over flying United (well, that and the drinks and somewhat improved vegetarian food).

It seems like 10 USD/EUR is about the impluse-buy point on net access for trips over 2 hours, and would make me more likely to choose to ride DB/Thalys over flying one of the many cheap airlines with whatever food I can grab in the terminal.