Why do they have to be anywhere near the railway? They are just a massive computer centre. They could be in Romania or India. Their location is irrelevant.A number of them do seem to be in rather bizarre locations. For example Manchester ROC being next to Ashburys station rather than Piccadilly, and West Mids SC being at Saltley rather than New Street or Rugby.
Can a ROC take on work for a short time for whatever reason from another ROC? Surely its just a matter of connecting the data feed to a workstation, or is it hard wired in some way?
I remember reading long ago (in Modern railways) when BR were building 'power boxes', that some interlockings had emergency panels. In case of comms failure a signaller could go to the interlocking and work from there while they fixed the comms to the power box. Is that still a thing?