It depends the context.
I would say there are 2 kinds of situations where you would use “vous”:

1. When you don’t personnaly know the person
2. When the person in front of you has an higher rank than you (at work, school, army, spiritually…).

In the first case, it is ambiguous because the proximity from which you can use “tu” is subjective. So some people will use “tu” even to people they only know briefly, and some people will wait until they are considered as “friend” before using “tu”. The difficult part is the time you switch from “vous” to “tu” (because you often see this person, and there is a moment you’ll consider you “know” him/her).

In the second case, the “master” may use “tu” or “vous” while the “pupil” will use “vous”. For instance, it is common to use “vous” when talking to your girlfriend’s parents, while they will use “tu” to talk to you.

These rules are not applied if one asks “on peut se tutoyer ?”.

Concerning your exemple, you may use “vous” if you’re talking to your more expercienced manager, and if he doesn’t want that, he will say “tu peux me tutoyer”.
If you use “tu” without asking, it may be considered as a lack of respect.
Where I work, the person who hired me said “Maintenant que tu es dans la boîte, on peut se tutoyer. Tout le monde se tutoie ici. Bienvenue”, which removes any ambiguity 🙂