Lets be honest, someone must have decided to build and fit out an overhaul works, without a plan to train sufficient staff to skill level required to utilise it fully. More a lack of joined up thinking.
They did, they went to 6 seperate labour provision companies, and then added together the numbers they got and said, "Look, we can get this many operatives available to work in London."
One may have wished to consider that an operative may be working for more than one of these labour provision companies.
And also may have wished to consider, the relatively low rates on offer by TfL might not be attractive, particularly as a large amount of other contracts requiring day-labour kicked off in the UK.
Then throw in the mix the other conditions that TfL doubtless needs and it's unlikely to work out. And yes, I mean TfL, not LUL, CLIP Labour was insisted on being TfL lead not LUL COO or LUL CoP lead.
Damn, done it again.
CLIP = Central Line Improvment Programme
COO = Chief Operating Office (Where trains and maintenance are done)
CoP = Capacity and Optimisation Portfolio / Programme (depending on when it was) (Sitting between Major Projects and COO).
TfL insisted on managing labour for the project as part of TfL Engineering for the project, and spinning up a fully separated team of Testers, Charge Hands and Labourers, rather than trying to morph the AC15 teams (Bakerloo Corrosion Repairs) or up-skill the TMU (Train Mods Unit) team who were working on D-Stock Rail Adhesion Train conversion and maintenance, 1962TS RAT maintenance, Battery Loco Life Extension and 750V works, and heavy repairs (Buffer Integrity Test Unit Rectification Work).
Because as ever, TfL knows best. (How's that Sub-Surface Resignalling now on it's 3rd attempt going?)
Not to mention the perpetual "need to go into production tomorrow" when the design is nowhere near ready mentallity.