Locating monument with OPUS vs locating CORS

I'm hoping for a general overview for a non-specialist. I know that a static observation with a GPS receiver can be post-process a file with OPUS to locate a monument relative to nearby CORS stations. When it comes to locating the CORS station itself, it obviously has to be a little different, because the location of the station must be available for any point in time, not just one 4 hour period.

But is there a fundamental difference between how a surveyor's monument is located and how a CORS station is located? Is the CORS station located relative to nearby stations, or something else?