I don't think the Escorted Excavation Squad is coming to save me
After what you said I think I can be more clear about what happened:
The Infestation spawned on top of me which I presume spawns in at the same time as the Escorted Excavation Squad. When the Infestation spawned it created walls around the Cogmind and one as-66623. I've left the game to run for 10000 time and haven't heard the Escorted Excavation Squad use their Grenade Launchers and the game didn't pause to play out those animations once in that time.
I'm not sure exactly what to do except abort the play-through as I'm stuck and have no way out.
I have a couple of ideas as to what might have happened:
1. The Infestation is still alive and stuck in the cave to the South. With no way for the Excavation Squad to get line of sight they won't attack the Infestation.
2. All but one of the Infestation died when they spawned on top of me and I killed the last one in the two space area I now call home. If the Infestation are all dead then the Excavation Squad are on a tea break.
I've attached another screenshot just to show the time passed.