What it sounds like to me is that it's a little bit of a weird system.
Subscription players get some amount of currency each month as a stipend (similar to STO + Zen), and full access to any "DLC" zones that are added as part of expansions or w/e. If their sub lapses, they lose access to all of those zones.
B2P players get access to the primary zones, then have to pay to get access to the new zones. Apparently that access is permanent once paid for but it's a little weird when contrasted with the subscription system, to me.
Might pick it up again when I get home though.