It's definitely not a 'new' engine, it was a hash of the Take on helicopters engine mixed with A2. All the latest blog posts say is they've redone rain effects and fog along with a couple of lighting tweaks.
I would feel a lot better about the whole project if they just said they were going to leave SA where it is now and start again from the ground up.
They were the days. DayZ, Epoch, Overwatch, Breaking Point, RP, Origins, Taviana, ArmA 3, Standalone, even Wasteland mod for ArmA 2 - I played them all religiously everyday for months on end. I remember it as fondly as my CoD4 Xbox days. Now I've grown up and have responsibilities, don't even own a gaming PC anymore... Aw to go back.
I played it once after I got it cheap through Humble Bundle. I installed it, setup all the mods etc. Logged in, spent quite a while setting up the controls/keys the best I could, just got to a point where I could play so I spawned in and got put in the middle of no-where, started to hunt for loot but found nothing then this guy appears out of the woods.
I just stood there as I had no weapons or anything, he ran by and said 'Hello' in a German accent, ran about 20m's past me, then around and said goodbye, then shot me in the leg. I bled out and died.
True story.