I'm not sure from a legal point of view any council can simply decide something like that - I'm pretty sure that the normal planning permission things would all have to be gone thru. MDC have certainly had it dismantled by Eavis at some point, and while I can't be sure when that was now, I'd guess it was between the 2005 and 2007 festivals. I'm not sure if Eavis has been made to take it down at other times since then, but I thought it had been.