https://geodesy.noaa.gov/CORS/IGb14/
Posted on the NGS home page. I did not know the US NGS network is now called NCN.
BTW, I am not an NGS employee and therefore not privy to any more details than anyone else. I probably check the site more than others...
More details:
Bulletin emailed by NGS on 15 May https://content.govdelivery.com/accounts/USNOAANOS/bulletins/28bc5b3
I think their lede is a bit buried, this affects only SOME of the CORS, those that also belong to the global IGS frame. Even the best coordinates are through time damaged by unpredictable crustal movement or station instability; this seems to show that
- the IGS tolerance for things going out-of-bounds appears to be cm level.
- when IGS pulls their carpet, at least some of the NGS furniture will move
Are the rest of the CORS inherently better? No, they just aren't maintained as rigorously; though many efforts are underway
- multi-analysis center REPROcessing of both the IGS and NOAA CORS networks preparing for ITRF2020 frame update
- patchwork repairs to CORS with notorious coordinate shifts, e.g., news/coordinates-puerto-rico-earthquake
- improvements to CORS short-term plots to highlight the difference between official vs real, and new ways to find the 'best' CORS for any given place + time