Confirmed, this is new section.
How did I verify it?
I did a backup of 1.0.0.10 game files when patch announcement was made.
Since Underrail does not use DRM, game can be started directly by exe, without Steam, which I used to start older version of the game.
Then I've gone south of Rail Crossing, with older 1.0.0.10 compatible save from my last playthrough, and verified that rail area has no area transition, unlike with new patch.