The building of it wouldn't take that long actually, a new build could be up in a little over 12 months from start to finish, the bit taking the time would be the design period, even if you look at the standard stages.
Stage 0 - Strategic Definition (2-3 Months) - Architect, cost consultant, Civils
Stage 1 - Preparation and Brief (Few months) Architect, cost consultant, Civils, MEP Consultant, Structural Consultant
Stage 2 - Concept Design (4-6 Months) Architect, cost consultant, Civils, MEP Consultant, Structural Consultant - Tender packges will go out
Stage 3 - Developed Design (9-12 Months) Architect, cost consultant, Civils, MEP Consultant, Structural Consultant (dependant of form of contract, contractors may get involved at this point to steer buildability in design. Loads of people involved at this point. There would be a huge amount of information getting out there is people needed/wanted to know. This would then be put the planning authority prior to cost commitment
Stage 4 - Technical Design (9-12 Months) A builder would be on board now and assume project responsibility, the Architect, if Novated, will work for the builder, not the Client, same with other consultants.
Stage 4a -Consulatants responsility and leads to Guaranteed Maximum Price
Stage 4b - Cost agreed and Builder takes responsibility for delivery - All now in hands of the Contractors with Consultant support. manufacturers on board
Stage 4c - Construction level detail of drawings and start of any off-site fabrication
Stage 5 - Construction (circa 12 Months)
Stage 6 - Handover
Stage 7 - In Use Limbs AOTS
It takes forever to get a project of this size off the ground. Now, in reality, Stages 0,1 could be done from anywhere in the word really, at a real stretch, stage 2. But site visits and visible work would have to start happening in order for the later stages to progress. That would mean the hiring of a company in order to do it.
Thats my thoughts on it anyway. they may have a way of doig all this and keeping it really, really quiet, but if they have it's a new on on me and would n't align wit the riba stages>