If any program can convert .sos and .bos files to one another and vice verse, it would by Dynamite VSP from which both of these file types originate. As to if this conversion is actually doable or useful, this could not be reliably verified from open sources.
Convert Dynamite VSP swept object style file to Dynamite VSP building object style.
We found one software available in the database for this conversion.
Microsoft Windows software - convert sos to bos on Windows
Program used to render 3D engineering design data
Convert from sos 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.