This V12 engine has existed for a couple years. I had a chat with
the company back in 2010. The engine was 6.1L (86mm bore x 88mm stroke), and they quoted an MCP of 480hp. It might be the same engine.
While a DI turbo diesel recip engine would definitely give excellent SFC, there are still some other issues to consider. The installed weight penalty of this complete engine system (including plumbing, heat exchangers, etc.) vs. a turboshaft engine is quite substantial. A recip turbo diesel engine would also require a heavier duty drivetrain to handle the cyclic torque impulses produced by the high combustion pressures. This engine would be quite expensive, and I could imagine it costing well in excess of $100K.
The project seems like an interesting engineering exercise, and the engine design seems to be well thought out. But the reduced SFC is not enough to justify the current weight penalty of the engine installation. We should also consider that the TE and SFC of small turboshaft engines is rapidly improving, thanks to better materials, improved compressor/turbine designs, and higher cycle pressures. So the turboshaft will likely continue to be the engine of choice for light helicopters.