Surely their portals would be intact, though?
Okay, order of events.
Parasol uses ELEPHANTs to destroy the whopping three megaportals Ballpoint has during massive assaults on these positions. While Ballpoint has better weapons and soldiers, Parasol overwhelms them with better airpower and plenty of expendable light infantry along with the beasts themselves.
Ballpoint survivors, thinking they can find a different out (and not realizing they're wrong and being there's only a few Asset Recovery units available, have barely any portal packs either,) sabotage the ones Parasol has, most of them being destroyed on activation. Since neither side brought more schematics than what would be needed to maintain thier combat equipment, both are left stranded or with only very small portals to get home, most of which are now unreliable at best without a Megaportal to bounce thier signals off of.
Eris had one in-dimension, and thier main base it attaches to is destroyed by a massive Ballpoint-Sewaturet-Stone Inc assault, with Parasol unwittingly being directed into their hiding places by a fourth party. Eris portals bigger than a single person are now rendered largely useless, making their small bases - now also in ruins due to this purge worthless beyond salvage and shelter to Ballpoint and Parasol.
Since both companies can build more vehicles and find more men, the survivors of the war on Everoc are left to rot by their corporate overlords. Being none the wiser and thinking they could still be rescued, they opt to make the most of things and carve out a place for themselves on Everoc.
EDIT: Okay, so I fucked something up in the raws trying to dummy out all of the large birds.
Did you guys know giant penguins could fly?