The last we heard about Mosler, the company, including the rights to its awesome but relatively unknown MT900 series of cars, had been acquired by Rossion, the former distributer of Noble products in the United States and the maker of the Noble-based Q1 supercar.
As far as we know, there are no plans to bring back the MT900 but there are still a handful of them around, including one very rare example in Monaco. This video from YouTube user PRonTheRoad shows a Mosler MT900 GTR revving its engine and then racing away through the tunnel running under the Fairmont Hotel.
The MT900 GTR actually started out life as a MT900 R race car but was made street legal by German importer Mosler Deutschland. That sound you hear is a 7.0-liter LS7 V-8 tuned to deliver a maximum 600 horsepower and 583 pound-feet of torque.