This form of ablution is performed by shrine people at a workshop, etc. It can also be organized by a shrine, inviting its parishners for spiritual training in the depth of winter.
神社関係者などの研修会等で行われる他、寒中に精神鍛錬の意味合いをもって、神社が主催し、氏子らを集めて行う事もある。 - Wikipedia日英京都関連文書対訳コーパス