If they can make this concept work then it is a brilliant idea. Not sure if it would be all that practical for long haul flights (which need more facilities eg catering, etc) but for short haul, eg trans Europe, this might well work, and could take advantage of quieter regional airports (provided they have or can be adapted to be rail served).
I would hope that it wouldn't be used for flying to cities that already have superb high speed rail links, eg London-Paris, London-Brussels, but for longer 'short haul' (if that makes sense) such as, for instance, London-Marbella, where high speed rail is less practical due to distance, and the need to change trains.

I don't see why this couldn't work on the aeronautical side. On the railway side, a lot of prejudice and established practice stands in the way of getting a flight-weight article permitted to operate on rails. At the very least, there will have to be detachable bogies to keep the modules light enough to fly efficiently.

Personally I'd be a little worried about travelling at 30,000ft in a pressurized fuselage that had been exposed to a railway environment, rather than the relative safety and caution of an airport.
I'd also be skeptical that those three little engines could move such a huge beast, given the enormous drag penalty of suspending three separate fuselages under a lifting body wing.

That might work in Europe, but here in "the land of the free" the TSA is going to insist on those long lines and other security theater measures.

I agree with piolenc, I think having it sit on a 'train dolley' would make it lighter since that part would not be lifted when it is hoisted up to the plane. It would make it lighter in weight. In comparison, it is like the containers that they put on specialized rail cars that can have them without having to add the wheels to the container itself.
I think this has a lot of potential. I think it could be a flying hotel for those traveling long distances. It could be the airplane version of 'shipping containers'.
I really like the blended wing design.
I think it could bring more people to train stations even if they are not really riding trains.

In my country they have torn up most railways. Railway tie boneyards all over Saskatchewan :(

Airplanes crumple and fall apart under the conditions railroad vehicles normally operate under. So the cargo/passenger compartments will have to be overweight.
If the airline wishes to be able to rapidly convert between passenger and cargo they can buy airliners in a convertible configuration. Configured for cargo they are a little heavy but not as bad as a rail capable fuselage.
The most efficient way to move passengers and mixed cargo is with a hub and spoke flight schedule, which is why you usually have to change planes one or twice on your journey. Overnight delivery services such, as FedEx could not afford to operate without it.
Do you want to get into an airline seat and then go to the airport wait until they load you on the plane then fly to your destination city and then wait to be put on a train then be transported to a train station before you can get up and stretch you legs without a real good excuse? I certainly don’t. Too many people die from sitting in airliner seats already.
It is a stupid idea that has failed before but there is always somebody who thinks "But if I was the one doing it, this time it will work."
http://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane

This idea makes less sense than its developers claim. The problem with rail plus air travel or indeed anything plus air travel are the delays as we wait for the plane, crew, and enough passengers to arrive. This doesn't solve that problem. Those in the first passenger module to arrive, for instance, will still have to wait for modules 2 and 3 to arrive and get attached. They'll still have to wait when weather delays the plane.
What it does mean is that those who're crammed into these modules will have to spend a long time in that same cramped and unchanging environment. That they won't like.
Remember, people get very upset over a 30 minute delay on the tarmac. They're going to feel much angrier if that's joined, in the same limited space, to a 2-hour train travel and airport sorting wait, plus a half hour waiting for the plane, plus another half hour waiting for the other modules to arrive and get attached. Add that up, and it's three hours in that module before the plane even takes off. And keep in mind the added hassle of boarding passengers who came directly to the airport. With three modules, two on opposite sides of the plane, boarding won't be easy.
Yes, it's no fun waiting in an airport, where travelers can get up, stretch, go to a less cramped restroom, and even dine at a meal that's likely to be more varied and less inflated in price than that on the plane. But that's still better than being stuck in a train plus plane module the entire time, forced to use its limited services.
The aviation industry needs to do more to deal with all the frustrations and delays of air travel, but this approach is hardly the answer. At best, it might suggest a minor but helpful improvement--the ability to check your luggage through to your air destination from major rail stations. That'd mean less hassle and fewer waits in line.
Years ago, I remember taking a train from Copenhagen to Stockholm. Those who ran the train must have thought themselves clever by having my train load onto the ferry for the trip. Personally, I was disappointed. I'd have rather have exited the train with my luggage, ridden the ferry, and boarded another train, with all the movement and change that entailed. Spending that entire trip in one module/train car was a bore.

I can't see how the the join between the undercarriage and the wings can be made string enough in this configuration. Also, how can you ensure that the wight of the two under-wing modules are the same weight given potentially different cargoes?
You would also need to know the weight of every module before fueling the aircraft.

It looks like it could do to what has already happened with shipping in containers, general cargo very feasible simple cylindrical containers.
But human transportation involves far more complex issues, security, sustenance, handling logistics, etc...