I'm no computer buff, so this is going to be in very simple terms. Is it exceptable to have all data/drawing files and manufacturing sub-systems for a plant being controlled by a head-office server? This head-office is not certfied to any standard.
Administration rights are given to only a select few at the head-office and they also do the back-up. The head-office has no operation procedures of work instructions.

I don't see any problem with this. I would have something that indicates they backup the data files.