[Hatman]

Great news and photos! It is so cool to see construction of this segment after so many years of waiting!

One thing I would add to this discussion of viaduct vs. grade-crossings is that VTUSA shares tracks with freight trains. Big, heavy, ginormous American freight trains. Building a viaduct for light-weight zippy electric trains is one thing, but building a bridge for the typical monster USA freight train is quite another.

Why share tracks with freight trains? Because that is absolutely critical to the profitability of this service. Remember, when Amtrak says it earns a profit on the Northeast Corridor, it only means an operating profit - specifically running and maintaining the trains. The tracks (as well as the bridges and tunnels and stations and all the other infrastructure) are not counted in Amtrak's profitability calculations, and if they were then Amtrak would have to admit a financial loss.

It is well known that VTUSA's entire business plan assumes they can make the same sort of operating profits as Amtrak's Northeast Corridor. But that's only operating profit! VTUSA would still lose all kinds of money if they had to maintain their tracks - but they don't.
The Florida East Coast Railway will still be running their freight service on the line, and the double-tracking projects that enable the passenger trains to run in the first place will also benefit the freight service. The 'All About Freight' people were not entirely wrong. Railroads have - both historically and presently - been most profitable hauling freight as compared to passengers. Throughout most of railroading history in the USA, passenger service was only profitable because of the mail service that ran at the head-end of most passenger trains. When mail contracts went to trucks and airplanes, private US railroads began a serious push to purge their passenger services.

...Anyway, what we will end up with is a highly-profitable freight transportation system with a lot of excess capacity. Empty tracks with no trains are an idle investment. Idle investments are potential money that is being lost. How do you capture that potential money? Run some passenger trains! Passenger trains are light and don't damage the tracks (comparatively). They start and stop quickly and don't get in the way of freight services - and on a completely scheduled railroad, such as the Florida East Coast (a rare practice among US Railroads), there won't be a lot of conflicts anyway.

Simplified, the freight trains pay for the tracks and infrastructure. The passenger trains profit off the excess capacity. Stations and other passenger infrastructure are paid for by other developments (residential and commercial towers, for example).

I find this model extremely exciting because it can be used by other railroads in very similar situations. Miami and Orlando are not the only city pair where this model makes sense. Once VTUSA begins to show a profits from its investment, I'm hopefull that there will be pressure on other railroads make similar investments in other corridors. For-profit passenger trains could stage a limited comeback in optimized corridors, and they could do it very quickly and with very little government involvement.
It is great to consider building a 70-mile concrete viaduct down the Florida East Coast. But to have passenger trains begin rolling now, or at least within my lifetime, and not just in Florida but also in California/Nevada and potentially Georgia, Texas, etc... That beats all hypotheticals and is worth a few grade crossings.
IMO, of course.