There isn't quite enough resolution on the photos to make out the leaves, but we can see that they are roughly almond shaped with a toothed or irregular edge, so hornbeam is probably a good guess, especially since it is well known for this kind of work.

Hornbeam is not the only tree than can be trained in this manner. Pleaching - Wikipedia, the free encyclopedia It is common to pleach mulberry in the mediterranean. But a key point is that it is a lot of work. Also it isn't much of a screen in the half of the year with no leaves.

The quickest and most reliable kind of screen is made of brick or wood or the like, also takes up very little space. Plants can then be put in front of it to decorate it.

You can also get a year-round screen just by planting a typical evergreen hedge, but you will have to maintain it. The trouble with really fast growing hedges is that they are more work to maintain in the longer runs. The trouble with sensible hedges is that they take a few years to get to the height you like. Some of the evergreen berberis are some of the easiest hedges, and occupying relatively little space as hedges go. Bamboo is another screen if you choose an evergreen kind, and is one of the few hedges that reaches a natural maximum height of its own accord. However it takes a few years to get there; is relatively expensive as a plant; and may need in-ground infrastructure to prevent it becoming invasive.