They already launched a "Loop" in Vegas, and it's a small tunnel with manned taxis running in it, operated by the city. And it took longer from project start to inauguration, per mile, than the Channel tunnel linking the UK and France.
So, the LVCC was built at 0.54 km/month, while the Channel tunnel was buildlt at 0.7 km/month.
Which part is false?
However, if we look at freight+people crossing the tunnels, the Channel tunnel surely wins again - it may be roughly 10 times more expensive per km, but it carries orders of magnitudes more, by rail + by car.