I understand the hard copies of the Comoros' accession documents are yet to reach OAPI. It is believed these will arrive soon but there is a little uncertainty pending their arrival.
The Union of the Comoros is due to become a member on 25 May 2013. From this date, applications filed in OAPI will cover the Comoros. Furthermore, renewals filed after this date will then extend the relevant registrations to cover the Comoros.
In the meantime, if renewals are some time away and you wish to protect your trade mark rights in this country, it is possible to file Extension Applications to cover the Comoros. (This is very much different from the CTM system where new members (such as Croatia) will be automatically covered upon their joining.)
Prior to its accession to OAPI, the Comoros was one of the Cautionary Notice countries of the world. If you have published a Cautionary Notice in the islands then you should now look to register these rights at OAPI either by making an application or, if existing OAPI rights already exist, by making Extension Applications (although if these rights are close to renewal you may be able to save some money by just waiting until renewal can be filed).
I have previously speculated that the Comoros may join OAPI because as a small, francophone country it would represent a quick-win to join this organisation. However, it is located between Mozambique and Madagascar in the south west of Africa and will form a geographic outpost of OAPI - they will need to enlarge the map appearing on their homepage. Saying this, Madagascar was a member of a precursor to OAPI, OAMPI.
The Comoros represents the 17th member of the OHADA - Treaty on the Harmonisation of Business Law in Africa to mirror this with membership of OAPI. The Democratic Republic of Congo (for those of you of a certain age, this might still be Zaire to you) is also due to adhere to OHADA. This country already has its own trade mark legislation and has less need to join up to OAPI too (although this did not prevent Mali and Guinea becoming OAPI members in the 1980s and 1990s respectively).
As one of the world's poorest countries, the Comoran government will be hoping that its accession to OAPI will encourage investment to the islands.
Incidentally, the Comoros disputes the status of Mayotte, part of the Comoros islands archipelago but administered by France (at the wishes of its local population it may be said). Mayotte is covered by French registrations (including International Registrations designating France) and, from 1 January 2014, when it will become an Outermost region of the European Union, Community Trade Marks too.