Unfortunately its not, yes framework is reused but business logic part is written from scratch most of the time and it is that part where most errors usually occur. That is why you can't just install SAP or Dynamics you need to program your logic and workflows into if first, the fact that framework itself is reused saves some time sure, but error probability increases with the amount of customization framework provides.

I'm talking about software designed for railway signaling, like SelTrac, not generic business platforms like SAP.

I don't know, but presumably there's still a lot of work

- planning and then (re)locating points/switches

- planning and then (re)locating signals or balises

- updating trains

- configuring the software to reflect the track and signals

- verifying the final configuration

Seltrac will not be accepted by MTA. They have their own CBTC specifications and Thales (seltrac supplier) is engaged in a large program to create a compliant product.