I tried to fly in to RCTP today (15 Sep 2024) during the RCTP Fly-In, but I kept getting directed to an approach frequency (125.10) that was not available to me. I could communicate with Taipei Center and with a separate RCTP approach frequency (124.20), but not the 125.10 frequency.
This made me wonder whether certain ATC frequencies are only available to participants who registered for the event?