Hmm, I talked with grid solar people who've been using this for a while about a year ago. Maybe this is a new version? Anyway, they were saying that it really helps in the winter when you can harvest the reflected light from the snow. But doesn't do a ton usually.
Yeah, but the people I was taking to worked in grid scale rather than utility scale, so in fields rather than buildings. You'd want to avoid paving over the whole field for cost, but also avoiding huge runoff. They are often also renting the fields for 20 to 30 years rather than buying them outright, so paving over the whole thing wouldn't be appreciated.