1. Any third party may, in accordance with the Implementing Regulations, intervene in opposition proceedings after the opposition period has expired, if the third party proves that
a) proceedings for infringement of the same patent have been instituted against him, or
b) following a request of the proprietor of the patent to cease alleged infringement, the third party has instituted proceedings for a ruling that he is not infringing the patent.
2. An admissible intervention shall be treated as an opposition.