The "cooperation":
Spoiler
The damage is distributed between Emitters, which means each Emitter heals part of the damage.
Spoiler
If you hit one with a few Nullifiers at the same time, it will break before it can pass the damage.
The "runner nest":
Spoiler
It really is harmless. It's special feature is roving, in that area only.
The "failed emitter"/"unbuilt spore tower":
Spoiler
It produces AC, but isn't worth extracting from. Hit it or it's parent (one of those on the bottom right) with enough beams to destroy.
Spoiler
There's a lot of regeneration here. You will need to turn off beams a lot of the time in order to charge for the next spore attack.
The "nullifier-proof emitter":
Spoiler
It's proof against Nullifiers (Wow! Who would have thought?). Hit another one of the sharing Emitters a few times, and it will be destroyed by passed damage.
No PZs: Just what I said in the intro. text. The sharing Emitters won't leave PZs.
Orbital C/AC:
Spoiler
When certain Emitters are destroyed, it will rain Creeper or AC. You have been warned.
The CN-sized broken fortress:
Spoiler
It does nothing. There isn't even any CRPL here. Patch it up if you are a completionist.