15.—(1) In any proceedings in which a devolution issue arises, the Secretary shall as soon as reasonably practicable by notice inform each of the relevant authorities thereof (unless the person to whom notice would be given is a party to the proceedings) and shall at the same time –
(a)send a copy of the notice to the parties to the proceedings; and
(b)send each of the relevant authorities a copy of the originating application and the notice of appearance.
(2) A person to whom notice is given in pursuance of paragraph (1) may within 14 days of receipt thereof by notice to the Secretary take part as a party in the proceedings, so far as they relate to the devolution issue. The Secretary shall send a copy of the notice to the other parties to the proceedings.