YES, for sure call her owners and check up on her, and if you see her back at your office again, take her and run back to your friend! I don't understand your buildings owner- what harm could a kitty do to the building or grounds that would make him want to get rid of her?
Here is a thought too: Maybe Tasha's owner should start reading Pet/Cat Talk. It gives some people a different perspective on cats. I know there are still a lot of people out there that believe cats should be COMPLETELY free to roam, no matter what the circumstances or environment.