Those users who need xmltvnz already have it. If the sources change so that the program needs changing there are no shortage of ways for Reven to inform users and make it available without having to post anything that contravenes the takedown order.
From then up it's up to the ingenuity of the user community to ensure an ongoing source of epg information.
It's what I would do but since I have access to free legal advice I might check with them out of interest. But there is no benefit in challenging the order since there are no commercial losses that Reven faces.