Head Coach and Pregame Meeting
 

Fed rules: The head coach is required to attend the pregame plate meeting, thus allowing him to remain on the field for the game. There are some exceptions to this:
1) He is stuck in traffic and is not able to arrive on time
2) He is attending a sick or injured player.

Are there any other circumstances?

Thanks

Oh, absolutely...
1) He's downtown pleading guilty to some unpaid traffic tickets
2) He's at his divorce lawyer's office signing papers
3) His massage therapist was running late and he's still at the salon
4) He's visiting his wife in the hospital and is running late (actually had this one happen)
5) etc, etc....

There are innumerable reasons that a coach could legitimately be unavailable. It's useless to try to come up with a definitive list - if he's available but just refuses, restrict him. Otherwise, don't worry about it.

Coach?
 

What about the game is being broadcast on radio or TV and the coach is being interviewed by the announcers. Is that a legit reason?

I would say "no" -- all that should be over well before the pre-game meeting.