I do not get this part. These are not advantages of tube v railway track, because a railway track can also be built above ground and can also be build from prefabbed sections. In fact I would think that building a railway track would be much cheaper than building an airtight tube.
Unless Musk has found a way to make the cars weightless, the tube must support the weight of the cars. Further, the pylons must support the weight of the tube and the cars, over a smaller footprint.
