I know my TOC does open advertisements that anyone can apply for. Obviously you’re more likely to get the job if you have front line railway experience though, because you know more about procedures and safety
Even on UK Rail Forums, staffed by Industry professionals and knowledgeable individuals, it has been stated that as an outsider (ordinary person looking for work) you have no hope of becoming a TfL tube driver. Promotion is from within, and only after x years of doing a job in areas such as front line customer service.
So 'closed shops' do still exist on the rail network.
I personally consider this to be a discriminationary union practice. As it shuts out any member of the public applying for a position, only those currently within the organisation will get knowledge of positions, and be allowed to apply for them.
The only positions the Unions don't seem to have issues with being advertised publicly are the lower end jobs, such as ticket gate operatives, and customer service. Anything higher paid is reserved for those already in, despite someone on the outside being more than qualified.