I am aware that FCC had an apprenticeship scheme last year, certainly included operations, may have included other things (my memory is slightly hazy)
It gave the impression of being a one-off recruitment exercise not an ongoing thing, but that's not to say they won't do the same in future years.
If you're considering your options for 16+ then it's probably going to be more use to you to look at what's available local to you, rather than look at options at the other end of the country. If you're London based (as the TfL reference suggests) then you'll potentially have more options open to you.
Best thing would probably be to contact (an e-mail would probably be best) the TOCs local to you and enquire whether they are likely to be running apprenticeship schemes in whichever year you're looking for.
Good luck!