I'm reasonably friendly with office cleaners at buildings where I have clients/etc (it's a way to practice my Spanish, plus I'm often there at odd hours, and it's a good way to evaluate some security threats.). Still, it's usually contracted out to outside companies, etc. (Same with security guards)

Actual janitors/facility maintenance people, on the other hand, are usually super interesting to talk to about maintenance/infrastructure issues, potential efficiency or other upgrades, etc.