Being at near ground level gives some options an aircraft doesn't have.
Plenty of air is centimeters away. The only trick is to get to it. Assuming the capsule is intact, and can come to a rest in the 10 minutes emergency air lasts, you just need a way to open a hole to the outside. Just pump all the air you need until rescue arrives.
If cabin pressure is normal, the easiest would be to have a hollow lance pierce the tube. It would take some work to jab though ~1cm of steel. Might as well use a pair of carbide tip lances (with side holes) jabbing at opposite sides of the tube fr counterpressure. An overcenter system (like a car scissor jack when fully extended) can apply massive force. Pop, pop, you have air in and air out.
If the cabin breached, the entire tube needs to be filled. Time to get out something with high energy. A cutting device (friction wheel, cutting torch, etc) can get the job done, but slowly. Faster and more compact would be some thermite charges. Toss 'em fore and aft. Crude, but effective. Shape charge if you are crazy enough.
Or if you want really fast, and independent of the capsule, put vents on the tube. They can be as simple as butterfly valves or as dramatic as explosive bolt hatches. Butterfly valves have the advantage of using inrushing air to slow or move a capsule. Hatches give a way for people to get in and out of tubes for emergencies or maintenance.