Don't really have a reproducible save for this but this is what happens:
Red Fog: All (quadratic)
Mods: PerfectInformation, Flankpreview.
Gunner hits ADVENT MEC on enemy turn with overwatch, leaves it with 2 hp. Said MEC goes into overwatch at a moderate distance (9 or so tiles). Gunner tries to sprint the overwatch, gets hit by a 47% overwatch shot from said MEC and dies.
Reload. Gunner runs the overwatch, MEC doesn't even fire on the same tiles used to sprint. Sprinting to tiles where the MEC can fire yields a 26% shot.