It applies to all new roofing work, domestic or commercial, whether new build or repair/refurb work.
For repair work, it will depend on the extent of the repair/replacement as to how much of the standard should apply. For instance, if replacing one ridge tile, then that could be just bedded down as per the existing ones. If the whole ridge needs replacing, then mechanical fix as per the standard would apply. Likewise for the other parts of the roof.
With regards to "applying", it is not law or compulsary, but a sign of good practice. It will only become an issue if a problem occurs because of not following the standard - eg a ridge tile blows off because it was not screwed down.
But, the standard has only been changed to compensate for the current poor quality of workmanship and training. There are good roofers about who do not have to fix ridges, or nail every tile or clip verges, and their work would last for many years after the plastic ridge and hips have gone brittle and verge clips come loose.