The new section resulted from the addition of Prince Edward Island (PE) and will become effective on April 1 2020 (not a joke!). RAC said its Prince Edward Island members have been working for some time to create a separate Section for RAC ARES activities there. The provinces of Nova Scotia and New Brunswick will continue to be in the Maritimes (MAR) Section.
To see a map of all the ARRL/RAC sections, as well as a ton of other good information, visit EI8IC's very complete website.