In a lot of rural places they have done this for along time. Where we live in Wales 3 piggybacks off the local Vodaphone mast and so we get a really good signal even though on the 3 website it tells us the signal is poor.
The posters are clearly missing a headliner. No idea what they are playing at.
"Come to our festival, we've only got two headliners so don't forget to buy a 3 Day ticket."
Unless they plan to go BIG on day tickets for the other day. Coldplay, AC/DC or whatever and treat it as a case of "hey we've got this event too".
Madness
Strange.