To the extent of my knowledge, in order to reduce lag, blockland uses a brick grid. Instead of creating a bunch of models for each brick (LAG!), it somehow uses it's magical powers to... erm... do something else.
The brick grid does not accept bricks that are sideways, for example, as bricks must conform to the grid.
The same goes for moving bricks (player-built vehicles). The brick grid was not meant to support movement of bricks.
Of course, I could be entirely wrong about all of this
