It was stated during Estimates by the CEO QR that they have enough trains.
See https://forum.bettertransportqueensland.org/t/when-will-revenue-services-commence-in-cross-river-rail/706/24?u=ozbob
Mr MELLISH: Ms Stapleton, do you have enough rolling stock at present
to operate Cross River Rail services without the addition of
65 new train sets to be built at Torbanlea as part of QTMP?
Ms Stapleton: I do not have the exact numbers in front of me but
from recollection for the preparation timetable, the soft opening
timetable and then three-car operations the required rolling stock
was going to increase from 114.5 to 119.5 to 122, roughly.
Now, Queensland Rail, as I mentioned, has access to 75 NGIs
as well as 60 six-car sets or 120 three-car sets of its own fleet
so that is 135 to operate the required timetable.
Estimates https://documents.parliament.qld.gov.au/com/SDIWC-1AF9/C20252026-4826/Proof%20-%20Public%20Hearing%20held%20on%2031%20July%202025.pdf page 103