(1) Where:
(a) an action is brought by the owner of the EL rights, or by the exclusive licensee, under section 27; and
(b) the action relates, wholly or partly, to an infringement in respect of which the owner and the licensee have concurrent rights of action under that section;
the owner or licensee, as the case may be, is not entitled, except with the leave of the court, to proceed with the action, in so far as it relates to that infringement, unless the licensee or owner, respectively, is joined as a plaintiff in the action or added as a defendant.
(2) This section does not affect the granting of an interlocutory injunction on the application of the owner of the EL rights or the exclusive licensee.