You have to pass your probationary period before you can apply for other jobs internally; it's nominally 6 months but it can be longer or shorter.
Internally, Night Tube Train Operator has come out at around the same time as it has externally. Full time T/Op campaigns ran in late 2014 and late 2016, and there is still a huge backlog from that previous campaign. As you will I am sure have noted, Night Tube is being a huge drain on training resources resulting in very long wait times for internal staff, as much as some on here will try to claim otherwise.
(Still have no interest in Train Op before the usual suspects pipe up.)
To be fair, the “drain” on training resources comes from the amount of NT T/Ops going full time which need to be replaced, and this has accelerated after the union dispute about NT on depot waiting lists being leapfrogged by Full Time trainees coming from the school now being mainly resolved (I believe last I heard they were still arguing over the fact that LU were only offering 1 day a week backpay for those who were leapfrogged and the union wanted 3 days - equivalent to the Full Time salary missed out on)
This was always going to happen, T/Ops union reps (who represent both TO21 and TO23 grades) are going to look after the interests of their members so if NT T/Ops are perceived to be being disadvantaged by LU they will not accept it in the same way they wouldn’t for the full time T/Op members.
Quite a lot of station staff are not happy about the situation, but then equally I’m told there is far more interest from CSA’s about NT now as it’s seen as the best way in to FT, especially if you are strategic with your depot choices.
On one line I know for a solid 16/18 weeks not one trainee coming through the school was Full Time, every single one was NT.