Programs like ABC BlackBerry Converter can help users to extract the contents of BlackBerry .bbb backups and exporting a broad range of various files from it, including plain text files.
Convert BlackBerry backup (post 2012) to Simple text file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert bbb to txt on Windows
A conversion utility for BlackBerry backups
Convert from bbb file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.