Finians go bottom and it goes on head to head between the other two as far as I know.
Here is the rule from the regulations.
- For the purposes of Rules 6.21(4)© / 6.38 T.O. 2016 the following shall apply to all League/ Championships, Leagues and Cups run on a league basis;
When teams finish on equal league points for Qualification for the concluding stages, or for promotion or Relegation, the tie shall be decided by the following means and in the order specified;
(i) Where two teams only are involved – the procedures as outlined in Rule 6.20 (5) © T.O. 2014 shall apply.
(ii) Where more than two teams are involved – Scoring difference (subtracting the total scores against from the total scores for) of the games where the teams tied on points played each other only. In the event that a team involved in a tie consisting of more than two teams had their finishing points total affected by a loss of points against that team on a proven objection, forfeiture of points for breach of rule / regulation, or by loss of points for failing to fulfil a fixture, that team shall not be included in any play-off and shall deemed to have finished in last place in whatever means is used to decide the tie. The procedures outlined in Rule 6.21 (4) © T.O. 2016 shall then be used to separate the remaining teams in the tie.