48:10 (default FOV)
...
Vert- indeed out of the box OR if any patch is applied ("beta" patch v1.03 is still the only one atm).
...
Hor+ thanks to Racer_S and his
FOV Hack for The Saboteur v1.0.
The "right" value depends on which AR you think looks best at the default FOV.
You might think that the more you see, the better - but bear in mind this is a console port (default 4:3 may be "Vert+") and LOD and clipping issues tend to occur at high FOV values.
1) Hor+ from default 4:3...
16:10 (FOV 180)
16:9 (FOV 280)
48:10 (FOV 1160)
2) Hor+ from default 16:10...
16:9 (FOV 100)
48:10 (FOV 1020)
3) Hor+ from default 16:9...
16:10 (FOV -100)
48:10 (FOV 940)