We understand there is an option for a further 25 NGR trains. An option unlikely to be exercised in view of the Governments build in Queensland policy, unless there is a local build consortium set up. This would be possible as clearly 75 NGRs are not enough trains to service the demands in 2024. A local build consortium could build another 50? But at what cost.
Don't forget there is never really 100% availability of a train fleet. So assuming 95% availability (realistic) 95% of 135 (present projected fleet) is ~128 and this includes the 200s which will be approaching 30 years in 2024 (12 three cars = 6 six cars).
Enough? Nope ...
Interesting thing was the original concept was 200 3 car trains, changed to 75 six trains in 2011! It is clear I think that proper consideration of Cross River Rail and service improvements was not taken into account at that time. Half baked as usual ...