It would allow them to join EFTA but not necessarily the EEA.
http://www.efta.int/About-EFTA/Frequently-asked-questions-EFTA-EEA-EFTA-membership-and-Brexit-328676
If the UK would re-join EFTA, would it automatically become party to the EEA Agreement?
Not automatically, as each EFTA state decides on its own whether it applies to be party to the EEA Agreement or not. According to Article 128 of the EEA Agreement, “any European State becoming a member of the Community shall, and the Swiss Confederation or any European State becoming a member of EFTA may, apply to become a party to this Agreement. It shall address its application to the EEA Council.” The
EEA Council takes political decisions leading to the amendment of the EEA Agreement, including the possible enlargement of the EEA. Decisions by the EEA Council are taken by consensus between all EU Member States on the one hand and the three EEA EFTA States - Iceland, Liechtenstein and Norway - on the other.