There's a deja vu moment in the latest study from Amadeus on the growth of European rail between now and 2020.
Lots of interesting stuff here, estimating how indirect channels (including offline and online retailers and self-booking tools) stand to benefit from the predicted growth in European rail travel - increasing from about 12% (2011) of all booking value to 18% in the next seven years.
Worth remembering that Amadeus has made a significant push for its rail capability in recent years, but still, rail operators have tended to distribute their own products through their own channels and the report says indirect channels could help foster partnerships and cooperation and ensure their presence across multiple channels.
And, then quite near the end comes the white elephant on the page - technology.
The report emphasizes how rail companies will become more customer centric trying to differentiate product and build relationships with customers, how key cooperation is - cross-border, cross-cultural and cross industry and finally, how important integration is:

"there is a clear need for a solution that can plug into all the various booking systems and rail providers' systems; with the intelligence to book and integrate a through journey on any given route and compare different operators and that can compare different prices operating on the same route"
Initiatives to create a pan-European train booking system have led to nothing thus far although there do seem to be some moves in the right direction in terms of partnerships and general cooperation.
Here's a graph on current airline/rail partnerships:
And all this is important because, if the report is to be believed, there's a huge chunk of potential new passengers out there for the taking with estimates of an increase in long-distance passenger volume in Europe of 21% by 2020.
Travel agents and travellers want to be able to research, compare rail and book options, prices, availability... and people seem to like travelling by train, but without the aforementioned cross-everything cooperation and integration, it will hit the buffers again.
So, just a little bit of development work to be done (not to mention investment) and that's on top of the other factors that need to fall into place such as the planned high-speed rail connections and new hubs.