The original XM Led was built around the release of Mothership. I am assuming that this station is being built around the LED ZEPPELIN: Definitive Collection CD Box Set release that is coming. A majority of the single-artist based stations that I have seen on XM have all revolved around a new release or project of some sort coming from the artist in question. I can't speak for the Sirius channels as I have heard they may be different.
Of course... there was this little snippet from the channel's description:
Led Zeppelin Radio | Now on XM 39 & Sirius 33
12:00 AM - 12:00 PM
A 24/7 celebration of the music and magic of Led Zeppelin. A handcrafted channel dedicated to everything Led Zeppelin, including studio albums, rare and archival concerts, interviews, and listener interaction. A continuous and mystical radio voyage into the past, present, and future of the mighty Led Zeppelin. Led Zeppelin Radio Now on XM channel 39 & Sirius 33.
Yeah... I know it means nothing, but its fun to point out these little tidbits!