bunzip2 to a different directory

You can use the other bzip2 tools:

bzcat foo.tbz2 > /another/directory/foo.tar

bzip2 -ckd foo.tbz2 > /another/directory/foo.tar

Note that if you want to untar it to another directory, you could use the -C option to tar:

tar xjf foo.tbz2 -C /another/directory