If you would like to extract the contents of an NT backup (.bkf) file in Linux, mtftar is a utility that translates a Microsoft Tape Format (MTF) stream into the tar format. You can pick up mtftar from the authors site at http://gpl.internetconnection.net.
To get started, download the source code and compile.
$ wget http://gpl.internetconnection.net/files/mtftar.tar.gz
Using this utility is straight forward, as shown in the following example.