Looks like a portable darkroom for industrial X-radiograpy. That’s what I did at my last job.
Any time gas or oil pipe is welded and laid in the ground, these guys are quick on the welder’s heels to X-ray the weld (similar to a dental X-ray) for engineering and insurance purposes.
I say for insurance purposes because after enough shit like the California PG&E blast, they actually archive the crap (rather than sign that it was good and throw the film in the hole with the backfill).
Besides if it was really Aperature Labs, I would assume that there would be other haz-mat placards, since “it turns out that ground up moon rocks are pure poison”.