>The system is what geologists call a fault-controlled non-volcanic geothermal feature.

These are quite common. Hot Springs National Park in Arkansas is a notable example. Most of the hot springs in Idaho are on fault lines, as are the hot springs along Highway 395 on the east side of the Sierras (though there is Quaternary volcanism in the region, it's not the source of heat), and through much of the rest of the Intermountain West.

This site seems to be unique for both the volume and the temperature of water, though. I'd be curious to know how far away the water originated, and how deep it goes before being heated. The crust in the area is not known to be particularly hot, as far as I know, unlike the Basin and Range of the western US where tectonic stretching and thinning of the crust has brought the hot mantle much closer to the surface and increased the geothermal gradient.