Blair - 17099 is indeed another ex-London Trident that is to be decapitated for City Sightseeing in Cambridge. So in answer to your question, Cambridge is where the pair at Walkergate will be heading.
83G/84D - The Period 8 fleetcard (just uploaded) will provide the answers; http://mbonwick.cu.cc/SCNW/Fleetcards/11/North East
However, the E400s you mention have gone to Slatyford, the ALX300s to South Shields (I think). The B12Bs have changed home to Perth, part of the East Scotland region.
That is 19151 but its hard to tell if its fixed from that angle ?
Sadly I cannot access this site as my computer dosen't like it, thanks anyway.
My fault, the forum software has corrupted the link.
http://mbonwick.cu.cc/SCNW/Fleetcards/11/
Then click on North East.
12065 broke down today on shields road byker
Unfortunate place to brake down, if you know what I mean