Here's what I know (I'm not a native speaker):
"Scheduled" can mean Time-tabled events (Present Simple) or Arrangements and Plans and intentions (Present Continuous)
Four possible, Present Simple, Present Continuous and Future Simple, Future Continuous can be used in your last example:
- The meeting with Bob starts at 2 pm
- The meeting with Bob is starting at 2 pm
- The meeting with Bob will start at 2 pm
- The meeting with Bob will be starting at 2 pm
The distinction can be this:
- A command or a determined plan. (Present Simple)
- An emphasis on the near future or the speaker's particular interest. (Present Continuous)
- A simple statement of a future fact based on present evidence. (Future Simple)
- Either a prediction about a future event or a reference to continuous event that can be expected to happen in the future. (Future Continuous)
Here's about "PRESENT CONTINUOUS FOR FUTURE ARRANGEMENTS":
The present continuous is used to talk about arrangements for events at a time later than now. There is a suggestion that more than one person is aware of the event, and that some preparation has already happened. e.g.
- We're having a staff meeting next Monday = all members of staff have been told about it.
Notice! The simple present is used when a future event is part of a programme or time-table.
Here's about "SIMPLE PRESENT FOR FUTURE EVENTS":
The simple present is used to make statements about events at a time later than now, when the statements are based on present facts, and when these facts are something fixed like a time-table, schedule, calendar.
- The restaurant opens at 19.30 tonight.
- The plane arrives at 18.00 tomorrow.
- Next Thursday at 14.00 there is an English exam.
Here's about "IMMEDIATE FUTURE":
A pattern composed of three elements: the verb "to be", conjugated in the present tense, + about + the infinitive of the main verb is used to refer to a time immediately after the moment of speaking, and emphasises that the event or action will happen very soon. We often add the word just before the word about, which emphasises the immediacy of the action.
- She is about to cry.
- I am about to go to a meeting.
Here's about "FUTURE WITH "GOING"":
When we use going in a phrase to talk about the future, the form is composed of three elements: the verb to be conjugated to match the subject + going + the infinitive of the main verb.
The use of going to refer to future events suggests a very strong association with the present. The time is not important, it is later than now, but the attitude is that the event depends on something in the present situation that we know about. Going is mainly used to refer to our plans and intentions or to make predictions based on present evidence. In everyday speech, going to is often shortened to gonna, especially in American English, but it is never written that way.
USING "GOING" FOR PLANS AND INTENTIONS
- We are going to have dinner together tomorrow.
- I think Nigel and Mary are going to have a party next week.
USING "GOING" FOR PREDICTIONS
- He's going to be a brilliant politician.
- You're going to be sorry you said that.