"Also, what happens if the mechanisms that contain the "Star in a Bottle" fail? Will the French Alps suddenly and catastrophically acquire a new valley?"

As others have said, this is hot fusion not cold fusion, so the answer is most likely it would damage some very expensive components. The holy grail of fusion research (which so far seems largely unachievable) would be fusion at something relatively close to room temperature (so called cold fusion), as opposed to this experiment where you're dealing with temperatures comparable to the heart of the sun. The reason that's such a big deal is that before actual fusion occurs on a hot fusion reactor, you obviously must first reach the target temperature which takes a not inconsiderable amount of energy to achieve, and then further energy to maintain. The trick to making hot fusion practical is to somehow get more energy out, than you have to put in to maintain those insanely high temperatures. Obviously if you can find a way to still achieve fusion at a much lower temperature the situation becomes much easier as you've got a bigger gradient to play with (I.E. it produces the same amount of power, but requires much less power to get it to the state necessary to produce that power).

In order to achieve the massive temperatures necessary they do a couple things. First, you're talking about an incredibly tiny volume of space that's being heated to these temperatures (think of this as the difference between boiling the ocean vs. boiling a cup of water). Secondly they reduce the pressure to near vacuum. Thirdly they maintain these conditions inside of a magnetic bottle which is necessary primarily to provide insulation, both for the fusion material (the hydrogen) and for the apparatus that are heating and containing the fusion material (super conductors like it very cold and must be very close to the fusion material, so you're talking a pretty steep temperature gradient here).

Now, assuming they actually get this thing working, it's going to consist of a very very tiny super hot ball of very very thin hydrogen gas, surrounded by a near vacuum, and then a shell of super cold super conducting magnets. If containment were to suddenly fail, that small ball of gas would very rapidly expand outward until it collided with the walls of the containment vessel which would most likely consist of super conducting magnets, and whatever insulating material they can find to slap between them and the hydrogen. But remember, this is a very tiny quantity of hydrogen and it's surrounded by what is effectively a vacuum, as it expands outwards it will rapidly cool and become even more tenuous. Some of the atoms my still be energetic enough upon impacting the containment vessel to pit it or otherwise damage it, but absolute worse case scenario they do some damage to the super conductors and the vessel walls. There's basically no scenario in which containment failure leads to anything that the average person would describe as an explosion.

Now, what I would personally be worried about, and would be far more destructive is not a loss of containment, but some sort of catastrophic failure of the super conducting elements. Still probably not something anyone would worry about outside the facility, but it has a lot more potential to do damage that might conceivably hurt someone in the plant than something like loss of containment would.