If 1886 uses a simluated 35mm anamorphic lens then it means it's about same FOV as a 18mm spherical lens (around 90). And they added lens distortion to "correct" the distorted horizontal view like a real anamorphic lens, thus causing the illusion of low FOV because the perspective is not as harsh as the high FOVs in older games. Switching lens between 35mm-50mm-70mm should be probable depending on the size of environment.
"Simulating" a lens in a 3D game engine = playing with the FOV and camera. They aren't actually simulating the optics and how the light interacts with a lense.