Most boring machines (the kind that dig, not the kind that make you yawn…), use a huge diamond tipped drill. In fact, Bertha, the machine that drilled the Chunnel (tunnel under the English channel) was 326 feet (99 m) long and weighed 6,700 short tons (6,100 t). The machine itself cost $80 million and its drill wsa 58 feet across.
Now comes some new guy who want to cut through rock with super heated steam up to 1,800 degrees to tear the rocks into pieces. Theoretically this is more efficient.
Its is neat and clever, have a look at the article. And extra points if you get this reference, this is NOT the steam drill that got beat down by John Henry.