I'm not convinced that the shift to ROCs will do much for capacity. For the most part, they'll still be controlling the same kit on the ground for the time being. Cab signalling might bring about a small increase in capacity on long stretches of plain line, but - even with moving block - it'll still be heavily constrained by conflicting moves at junctions, trains with different speed profiles and so on. Under lineside signalling, four aspect, headways of three minutes - even less in a couple of lower-speed examples - can be readily achieved. How many routes come close to requiring this sort of plain line capacity at present? Most don't, partly because there aren't that many paths across a key junction, or because a stopping passenger or slow freight eats up a lot of capacity twice an hour.
Where it'll come into its own, I think, is with the rollout of TMS, which seems (from what little we've seen of it) to be a potentially excellent tool to aid decision making and the recovery from disruption. I understand that it's not necessarily to be limited to ROCs though - it can be implemented in existing signalling locations, albeit perhaps without the ability to do the signalling itself.
The incident with gas cylinders at Kings Cross and the evacuation of Three Bridges (the existing panel, not the ROC) seemed to cause their fair share of chaos. Taking out any single key point of the network is going to cause a lot of disruption across a much wider area, even if the eggs are well distributed across several baskets! On that basis, it seems to make sense to concentrate on making a single signalling location as resilient as possible rather than relying on the false sense of security created by having many different locations, each with the potential to cause widespread problems.
