We are all fixated on depots but couldn't Arriva just simply have a 'sign on point' in Newcastle City Centre? The only issue with this would be bus storage. Depending on the drivers duties, the buses could be ran to/from the depot by another driver who is going back to Blyth anyway.
I don't know that part of the country at all, but having been involved in scheduling elsewhere, I'm not entirely convinced.
Having a remote sign on / off point (possibly combined with a canteen / mess room) does occasionally work - depending on the length of route, having meal reliefs at a remote point (and a small number of drivers based there) can make the duties more efficient (a simple example would be a route where one round trip is not long enough for half a day's work, but two round trips would be more than a legal spell of work - in this case, each duty being 3 round trips, with the meal break at the distant end of the route after 1.5 round trips is ideal.)
But the number of middle duties that would naturally end up as both starting and finishing at remote point is likely to be less than you'd imagine. And of course there's a cost of having premises in the town centre for this, unless you go for completely remote working and sign on / off via smartphone or whatever.
Another option of course is to force drivers to sign on at depot and off at remote point (or vice versa) which tends not to go down very well, as (unless both sites are well served by public transport and / or early and late staff buses that go to where drivers live) this effectively adds a chunk of unpaid travelling time to each driver's working day. (I believe this is part of one or two current disputes in the industry.)
Also, there are practical issues with such a remote sign on / off point - is it big enough to warrant a supervisor? if not, then drivers are booking on with no oversight of whether they are properly dressed and not obviously 'under the influence'. And if it gets to duty start time and a driver has not reported on duty, and the depot that might have a spare driver or two is several miles away, that's a journey lost and a bus stranded. And then what about drivers paying in / handing in lost property (and so on) when they sign off at remote point?
I understand there are a few routes in London with some element of remote working (or where there is an allocation of a few drivers but no buses at a garage at the end of a route remote from the operating garage) but paying in cash is not something they have to think about.