In case you're wondering why the good old Greenwich meridian had to change - it's not a French plot but rather due to satellite technology.
With all the continents moving about the place if we had a meridian that was fixed with respect to a lump of rock then it would move all over the place from the point of view of a satellite - not much but when you're trying to do sensitive scientific or surveying operations with respect to GPS in America you can't have 0 degrees moving about the place in Europe.
The IERS meridian isn't fixed to a point on the Earth's surface but lots of different observatories around the world send in data and it's fixed based on that