Suppose Alice is leading an activity and has organized a meeting with the technical staff that will be working on the activity. The purpose of the meeting is to parcel out tasks, determine schedules, and other technical stuff. Alice's coworker, Bob, gets wind of the meeting and wants to attend. Instead of asking Alice if he can attend the meeting, Bob goes to one of the other meeting attendees and asks them to forward the calendar appointment. Alice first learns of this when she gets an automated notice from the calendar program that another attendee has been added to the meeting.
Is Bob's behavior acceptable? Would any of the following additional circumstances make a difference to the answer?
Bob is the lead on project that is funding the activity (but has delegated leadership of the activity to Alice and has not otherwise been working on the activity).
Bob is Alice's line manager (but has explicitly appointed Alice the leader of the activity).
Bob has been on leave since the activity started and is not up to date on the technical details. Therefore, he wants the agenda to be amended to include a catch-up briefing.
I'm interested in this question primarily from a business etiquette perspective. Obviously it's a manager's prerogative to attend any meeting in their department that they want to, and probably any coworker could get away with it unless the meeting deals in restricted information. What I'm wondering is, is it reasonable for Alice to feel aggrieved that Bob did not consult her about attending the meeting? In the cases where Bob is an authority figure, is it reasonable for Alice to feel that her stature as the leader of the activity is being undermined (i.e, that Bob might be seen by the rest of the team as revoking the authority that he previously delegated to Alice)?
Clarification: I'm trying to describe several variations on the same scenario. In the base scenario Bob and Alice are strictly peers. In the first variant Bob has some authority, but is not technically Alice's boss. In the second variant, Bob is Alice's boss. The third variant could be added to any of the variants already discussed. (One answer below jumped straight to assuming variants 2 & 3 were both in effect, which is one possibility, but not the only one.)