Boring Co's tunnel machines are just customized versions of existing machines. At best they are slightly faster than they base machines, and only in specific soil conditions.
However, as demonstrated by the Hawthorn and Vegas tunnels, the Boring Co machines are, in practice/in the real world, no faster than the non-customized machines, while at the same time yielding significantly lower quality tunnels (referring to the concrete shell built to protect the excavated portion of the tunnel).
And here's the crazy thing: if Elon had actually done his research, he would have known that the "automated digger" Boring Co plans to build already exists. They're just really expensive, because digging machines are built to-spec for each project based on soil conditions. These existing machines can be powered by multiple sources, though generally they aren't electrified due to the demands on the local power grid. In a nutshell, you'd have to build a dedicated substation to handle the electricity draw; the only reason Boring Co's tunnel machines don't is because they dig small utility-sized tunnels rather than large transit-sized tunnels.