Very, very unlikely. The company doesn't even have technical writers anymore for internal projects, let alone technical historians. And with the time it's taken and normal staff turnover, I doubt that there's anyone who really could write about the whole effort based on their own experiences.
Basically, it consisted of building of building a new central datastore for our content (that was pretty mature by 2005, when I started). Then hundreds of smaller projects to migrate this or that process to read from or update the new datastore or keep it in-sync with the old one. There was also a lot of opportunistic piggybacking of new feature work onto migration projects or migration work into new feature work. However, I only have the view of a regular developer.
I wouldn't say it never happens, but it certainly takes a couple tries and a lot of time and money.
My employer is close to being off our mainframe(s), but it will probably take at least another 10 years to get rid of the last little dependencies. We've already spent about 15 years (with hundreds of developers) getting to the point where all the major online and batch processes have been reengineered and have very small mainframe dependencies. The mainframe development teams are very small and mostly focused on decommissioning work.
But yeah, it's a massive undertaking. In our case, the business was motivated to pay for it because mainframes just couldn't scale for our main use cases.