There is one stretch of the new war quest where you need basically sit around in your railjack shooting fighters as some dialogue happens. That's about the only thing that's practically required.
Other things behind railjack - Ash & Oberon drops where moved to railjack, Sevagoth, epitaph, a handful of weapons drop from the caches of railjack missions, the tenet melee weapons require a resource collected from railjack void missions. Also, liches require a quick and simple railjack mission before the final confrontation - but that can be done on public with a random squad.
That's about it i think?
