Philip G Graham
Yes, more encouraging. There seems to have not have been an announcement as to which TBM manufacturer is to supply these yet.
For the initial assembly of the TBM there needs to be an external cradle structure to support the circular shape of the the shield until it starts its penetration. The TBM back-up is the name for the trailing support equipment which runs on either wide gauge rails or rubber tyres on the ring surface - behind the actual boring head, and is where the ring segments are placed in position. After each ring is completed, the TBM hydraulically thrusts forward off this ring, boring the next length by a similar width of the ring. For the initial launch a frame structure is used to enable something for the TBM to thrust against until sufficient rings are in place. Advance rates are usually quoted by how many rings are placed daily, weekly, etc.
If there is to be a construction railway delivering ring segments, then it will become apparent when the back-up is being assembled, if this is within public eye view. Is the Marrickville site reasonably open? i.e. not down the bottom of a deep shaft? The conrail or the MPVs run directly into the interior of the back-up.
I would say that the Melbourne sites are going to be much more confined, but this does not necessarily rule out a conrail operation.