Getting a tank into a basement is easy - at worst you just put a big hole in the floor above.
Getting a tank *out* of a basement, on the other hand, is potentially much more challenging.
Occasionally you see a news story about a bloke that's built a car/bike from scratch, often where his kitchen table used to be. They tend to have lost their wife along the way, only to find they're going to have to knock at least one one wall out of the house to get their creation out.
Someone I know very briefly had a similar experience in his garage, but that's only because we spot welded the garage door shut to wind him up (he used to go in through a side door to work on it).