Prof Stephen Temple
It is perfectly possible for one UK mobile network to back up another without creating a domino effect. There are two solutions. The first is an official "telephone preference scheme" that has been around for years for the fixed network for a time of national crisis. This is where critical uses can be identified, put on a register and MNO's obliged to have a dormant contract with a second mobile operator to take over the "priority user's traffic" should the mobile network they subscribe to go down.
The second solution is a commercial solution where the automatic back-up on a second network is a premium service anyone can buy into. The price of the premium service is set so that the number of such premium customers can be handled by the second network. This commercial approach is a dream solution - critical users have peace of mind and mobile operators have a new stream of revenue that is literally money for old rope. What is there not to like about it? Ofcom could do everybody a huge favor by mandating every mobile operator offers a premium back-up offer to their customers.