There are some positions that come up during the year, but I don't know about "I need to get out because of _______."
In fact, since they are both members of the ATA, your friend will have to be very careful (in a professional sense) how he or she handles this. I would strongly suggest, if they don't know how to handle this, that they should consult the ATA about how to deal with this issue.
It would be of utmost importance that no names (either theirs or the principal's) are mentioned during such a call. They may suggest that the first course of action would be to speak with the Principal to try to sort things out.
Do you know what your friends' contract status with the CBE is? If you wish you can PM me but there are many teachers here (I happen to be on Paternity Leave) that might have other ideas as well.
Here is a news article from the ATA News that may be a bit helpful in this case though it doesn't seem to mention how the process got started specifically, though the "The Implications" section at the end does illuminate a bit.