How to get operations-lift to Floor 3 - Rapid Launch Control?

After 5-10 hours of exploration - found it. In short - drop into the hole at the outgoing train station and explore (at this point the exploration is straightforward).

In details:

1. First of all, if you haven't found the train to production B, you need to do it:

   Go out from Ops on second floor, turn right and walk around ops, downwards, after couple of turns you will see acid area and a drop to a treasure. Take this drop and drop further untill you reach a floor. Then explore the area. The area is pretty big, but exploration is straightforward and eventually you will find a new train station.

2. At the end of this train station this is a hole. Drop there. Then, go forward, kill few enemiesa and you will face a broken exo-lift, drop there as well and pick a treasure. This is what I've found most hard to find (or rather understand that it is dropable).

3. Now you should see two strong enemies and a power conduit. Take a small drop down to them and overload the conduit. On the other side of the room there is a stairs and a closed door, go past it, turn left and take exo-lift. There will be a panel to call the ops to floor 3.

4. You can find the ops nearby, just do a little back-tracking.

This playthrough, shows steps 2-4.

But note, you don't need to get ops to the floor 3 to finish the game.