NR absolutely need to make use of external consultants all the time as they don't have the ability to provide every requirement of a project in house; NR aren't a construction company. Even before you start building you need feasibility studies, ground condition reports, ecology studies etc. Then you need all the different levels of design, then finally the construction.
A lot of aspects will be procured via frameworks which have been competed and have ceiling rates, to control costs. Each requirement then needs to be competed for (depending on many different criteria) which then gives you another element of ensuring value for money.
Sure, a railway project is likely to cost more than a high street project due to the additional engineering/assurance requirements, but there are plenty of requirements which can, and are, provided by non-rail contractors as well.
A lot of aspects will be procured via frameworks which have been competed and have ceiling rates, to control costs. Each requirement then needs to be competed for (depending on many different criteria) which then gives you another element of ensuring value for money.
Sure, a railway project is likely to cost more than a high street project due to the additional engineering/assurance requirements, but there are plenty of requirements which can, and are, provided by non-rail contractors as well.