There will of course need to be people to design the DOO systems, and produce the cameras that are given to the train maker to put on the train - and someone to produce the interface to make it work with the train management system etc, but there will be fewer people than the people replaced, especially if said trains are going to work for 30-40-50 years.
And those nice UK jobs for people making equipment for trains might be wiped out when we decide that we can buy in cameras from a company abroad, for less money.
That's the other problem we have to face - there might be 'other' jobs to do, but will they all be over here given we are increasingly becoming a service industry and those services can be provided from anywhere in a lot of cases.
Jobs like electricians, plumbers and fitters can still command good money, even with increased competition from people from elsewhere in the EU. But how many jobs like this, where you can't replace people with machines or outsource abroad, will there be in the future?