The protections were agreed upon in the heads of terms document drawn up to enable at time of the takeover. That was agreed between FPS and DFC, effectively DFCSS at that time (just as DFC is now effectively FPS). It was a key document that was enshrined into the DFC AoA and i think de-risked the takeover for a lot of fans.
I had a lot of criticism for DFCSS at the time and how they managed the takeover but they were diligent in securing the entrenched rights for the fans