The RIPE NCC has prepared a draft document titled "De-Bogonising New Address Blocks":
That is a misleading title. The problem is that ISPs cannot react quickly enough to open filters when new ranges are allocated. The proposed solution is to provide advance notification. I suppose this could allow ISPs to open filters before the new addresses are actually in use officially. However, it will also allow spammers to announce this space and get it through bogon filters. The real solution to this problem is to make it possible for ISPs to closely track RIR allocations in their filters in a semi-automated way. There may still be a few days of delay before a new allocation is fully routable but ISPs can compensate for that with internal processes. Why can't ISPs subscribe to a feed of all new RIPE allocations in near real-time? --Michael Dillon