How did you get the idea that this was ´in the agreement?´ AFAIK the very few trains running onward along Paris were never-a purely commercial venture, only on some peak-travel days and going onward to (winter) ski/snow places and (summer) the bright sun+sea. None of these trains ran at all during the main period of covid-the first to be scrapped completely.

Passes are also not at all accepted on the long distance Thalys that make comparable longer runs along Paris on the same base.

I assume a maybe better informed forum like railforums.co.uk may have more knowledgeable people for answers.

So it was never possible to book Interrail reservations to Disneyland? Huh?

Also, I am not sure what you mean about Thalys? The two outer Paris stations are reservable on Thalys to and from all direct destinations. The only reservation not for retail is the 11 minute run between them. Plus, Thalys doesn’t run services calling at CDG Airport or Disneyland to beyond Brussels; they all stop there.

I really think that is inaccurate about the Thalys, sorry. Thank you for the tip about railforums.co.uk.

That can't be true. Belgian railways explicitly state in their terms and conditions that the pass holder fare is available for London - Marne-la-Vallée (nl / fr / en). That also means that they are required by law to have a way of booking them and that availability should be such that you can realistically book one. They must at least have been available at some point (probably pre-corona). Maybe someone forgot to load them into the booking system. Or forgot to change the terms & conditions...

You could ask their Facebook team how you can book them and when they will be available on their booking website. If you do that, do let us know what they say.

I have written to SNCB-International via the contact page on Facebook with those questions and some background. Thank you for the excellent suggestion. Will update when they come back.

Having spoken to SNCB-International, who were exceptionally helpful, the fault in the online booking applet will be fixed. It is possible to call to book these tickets; except for travel in the next two months. I managed, after a lot of kind help, to book one this morning for early September. 

Availability is loaded, just inaccessible online because the booking web applet cannot select London to Marne-la-Vallée. But there is absolutely zero availability for the whole summer until September because the few Eurostar trains on this route are almost sold out for normal revenue tickets.

SNCB-International have promised to fix the web applet for booking Eurostar reservations allow direct bookings between London and Marne-la-Vallée. 

There is also fault on the interrail.eu side, which incorrectly sees zero availability for the whole year. Perhaps - I presume - because actual ticketing may be done via the SNCB-International online system in the backend - the fault is of course that it cannot ticket these journeys until the b-europe.com applet is fixed. Who knows! When SNCB-International fix their system, we’ll see if the interrail.eu one also works; hopefully it will.

Thank you @rvdborgt for your advice. The main thing is that these tickets are bookable by phone for anyone who wants them going forward. The ability to book online will apparently quickly return, though no exact timeline.

Happy travelling!

Thanks for having this sorted!

It's very well possible that Eurostar reservations on the Interrail website are done via NMBS/SNCB, since they also do some other reservations that way. It's e.g. the reason why a lot of optional reservations are so expensive via Interrail: NMBS/SNCB already charge 6€ per seat and then Interrail add another 2€.

Thank you! 

Haha, you are definitely right about prices! It must be fantastic profit though!