It can and has been done, as have been discussed here.
However, the youtube video posted in post #11 is an excellent example of the following point (already made in post #20, BTW):
By the time you mitigate all the weaknesses of burying a shipping container, you could have had a bigger and better underground structure or a same size structure for far less $$$ if you had just started with the appropriate materials to begin with. To whit: concrete (poured or blocks), steel, fiberglass or plastic tanks (designed for burial) or even culvert.
The buses that were buried in Canada were internally braced prior to several feet of concrete being poured on top of them, these braces were left until the concrete cured. The curved nature of the school bus tops gave the upper concrete structure (along with steel reinforcement) to carry the dead weight above. In other words, the buses only formed the shell/mold for the concrete, the buses don't carry any weight, nor could they.