There is no technology that would allow you to have a level-grade crossing on a high-speed rail track and be safe. It doesn't exist. No one in the world has come up with that yet.
There are lots of ways, and it's quite routine, that you can bury the rail line somewhat, so that the fencing and other things you need are not as intrusive, and make it cheaper to do the overpasses because you don't have to go up as high. There are lots of those sorts of things that you can do.
On a high-speed rail corridor, it's light rail that you use, and depending what motive structure you use, it doesn't necessarily have to be as wide as a heavy train dual system. You can run the trains closer together, so that you don't have to use as much space.
So there are ways of mitigating some of the costs, but there's no technology that we're aware of that would allow you to maintain level crossings. It just doesn't exist.