How often do mathematics professors move up from mediocre schools to good ones?

How often do mathematics professors move up from mediocre schools to good ones?

For example, let's say someone did some ok research at a postdoc and then went to industry for 10 years and afterwards got a professor position at a very mediocre place where they started pumping out solid papers over a few years.

Given that they had the talent to get a top 50 research school position on a traditional route, what are the chances that they get there in this situation?