For what it's worth, several magazine pieces have said they will build the railway in pieces as the route becomes ready and join it up later, rather than use the "head of steel" approach from a base starting point.
The haul road along most of HS2's length means they can do a lot of things en route, so to speak.
We still have the access at Calvert as the only rail access until a WCML connection is built, but The Planner was hinting that there might be access at Washwood Heath, where HS2 runs alongside the Midland line, to deliver rolling stock.
No contracts have yet been let for the "joined up" railway, so nothing is yet fixed.
Timewise, the progress of the slab track base installation will be the first stage of building the railway.
EDIT:
I see the concrete plant to build the Delta junction viaducts started production today.
So that must mean that the full Delta junction is going to be built for Phase 1, if not the connecting line on to Handsacre.
Production of nearly 3,000 viaduct segments has begun at HS2’s purpose-built open-air factory in Kingsbury, Warwickshire The segments will be used to build a network of 9 viaducts in the West Midlands Around 1,000 people are employed on the 55,000 square metre site Video explaining more...
mediacentre.hs2.org.uk
HS2 has started production of 2,742 huge concrete segments which will be used to build the Delta Junction, a triangle-shaped series of viaducts that will take high-speed trains between London, the Midlands and the North.
The deck segments – which each weigh up to 80 tonnes – are being made on site at a purpose-built outdoor factory at Kingsbury, Warwickshire. The 55,000 square metre site employs around 1,000 people in total, with a team of 200 tasked with building the network of 9 viaducts at Water Orton and Coleshill, crossing motorways, roads and footpaths. It also hosts a Skills Academy to support local people into employment or further training.
The pre-cast yard will turn out up to eight segments per day, with a variable weight between 50 and 80 tonnes. The segments are 3.5m high and come in two different widths - 7m or 11m, to support single track and double track sections of the railway.
