The point I am making is that everytime the discussion of passport controls an Eurostar comes up it always seems to be an impossible task to sort out, yet, other countries have managed with international traffic. The point of using the Helsinki-St.Petersburg/Moscow example is that you have a very good example of how it can be managed well.
Authority of border guards etc can be sorted out with approriate agreements/treaties between the countries - which I think is in effect regarding policing and Tunnel/Eurostar trains IIUC?
Does anyone have the illegal immigration and refugee figures for passengers travelling via the Channel Tunnel per mode of transport?
Nothing is 'impossible' - however, doing it at a reasonable cost, both financially and politically, is completely different. It would be very expensive for UKBA officials and Security to be riding each train from Paris or Brussels to Lille, checking passports and locking up illegals for ejection. No doubt this would involve a certain amount of confrontation, and manhandling of reluctant ejectees. Are we really prepared for that? No. It could be done, but expect ticket prices to increase substantially to pay for it. Trains coming from other places would have to have UKBA officials boarding somewhere else - probably doing one train per shift, including lots of expensive allowances etc.
Alternatively, Eurostar trains could be scheduled to wait at Lille Europe for about 30 minutes during which time passport controls could be carried out, and any illegals ejected from the train (with the same confrontation and manhandling - just a little easier with the train stopped.)
Of course this would not get round the 'screening baggage' rules for passage through the Channel Tunnel, which is the other thread to this issue, So, everybody to get out at Lille, train to wait 60 mins to go through passport and security check, as is done now on trains not originating at Brussels or Paris.
Much cheaper and easier to check passports and screen baggage before boarding, even if this economically means trains only coming from a small range of stations.
Politically, I cannot imagine that the UK would be prepared to entrust ejection of illegals to a foreign police force, before they could 'land' on foreign soil, nor expect co-operation from French forces if our own border officials/security guards do it. Maybe a treaty could get this co-operation, but at what political cost? What quid pro quo assistance could we possibly offer the French? Nothing I can think of.
The border guards at the Finnish border are not faced with third country asylum seekers or illegal economic migrants coming from Russia, which Russia then refuses to take back as they are not Russian Nationals. It just does not happen [ Russia has a long history of ensuring its own population does not just 'emigrate', and certainly does not permit transit illegal economic migrants or asylum seekers] . If the Finns were faced this situation, the through International trains would stop very, very quickly.
Asylum seekers and illegal economic migrants very rarely come to the UK by train due to the current stringent controls, which pretty much rule out the economic operation of Sleeping Car trains.