It's passenger rated in the sectional appendix. But it doesn't matter if it didn't even see any regular traffic (which it did, before the upgrades there were regular freight trains on the line), the fact it's officially an open and active line means the processes are a lot simpler as it's upgrade of existing track not putting down new stuff.
This service did trigger a whole host of upgrades such as signalling, level crossing, linespeed and obviously new platforms, so it has needed a fair amount doing. But it's been easier than it would have been had the line been ripped up.