Just outside the main building, facing toward the long upward ramp, behind the stacked crates.

These two are easy enough to check back-to-back, in the main building. The exit can spawn at either of Null's incubation tank regulators.

At the top of the ramp opposite the first check, where the first mission marker spawns in MPO.

Directly next to the large stack of crates on the bottom level, on the spawn-side for the first trip to the Research Lab in MPO.

These two are the furthest checks, on opposite sides of the map, where you spawn in for MPO.