The regions involved vary wildly, depending on where infrastructure needs auditing (either because of catching up on the utility's own documentation, or updating a competitor's docs that they're buying out). Medium to large cities of differing climates.
People in this role either choose to remain in a region for around a year, or move to various areas as a perk/"vacation".
I was introduced to it by what I found out to be a really disorganized and mildly unethical group, which is why I'm not currently out doing it!; looking to forge a new group with trustworthy people, who also know what a damn computer is!
*(but, if you're reading this and strongly interested/motivated, you may be able to assist on the documentation side or more!)
Here's a couple of pics from one of the access roads on one of the runs I did: https://ibb.co/B4WWM8k
The crux of the concept is receiving a map, sometimes partially completed, sometimes with partially incorrect information, and using easily placed symbols to make corrections for submission.
Whatever % of that you feel comfortable doing in the field, you do, with the remainder being finished wherever (often in front of a TV show, from what I saw).
A slightly more complicated (and nonpublic) version of contributing to OpenStreetMaps.