Knight:

You are correct - the county board also has the right to dissolve a branch. If that decision is appealed, it goes to the Provincial Council. Though it is not explicitly specified, an appeal from that body would presumably go to the Ardchomhairle. However, no matter the powers explicitly enumerated to the County Board, I believe that the quote I mentioned (explicitly giving the Ardchomhairle jurisdiction over "all matters of discipline") is pretty unambiguous - the Ardchomhairle, as the highest body, definitely has the right to take that step.

Regarding natural justice, as it happens, I believe that all branch members have been notified about the new branch being formed, and of the opportunity to participate. I wouldn't personally be at all averse to the new branch deciding to hold special elections, just to enhance the legitimacy of the new group.