> However, in the public Google calendar I can set up alerts for all the meetings someone else has (useful for secretaries etc.).

The fact that you can do it doesn't mean it is proper for you to do it other than as reasonable for legitimate job duties.

There is no system in place physically preventing me from doing lots of illegitimate things in my workplace, but that doesn't mean that if I do them I get a free pass merely because it was possible to do them.