Well there are a lot of answers for how researchers do this, and it will depend on the data source and intent of the project.
1. For background on what others have done, I'd recommend starting with flosshub.org
paper database in addition to your normal literature search tools such as Google Scholar or ACM dl.
We have the tags 'bug reports' for example and a long list of papers to be downloaded there:http://flosshub.org/category/tags/bug-reports
Keep in mind that any papers on flosshub are about FLOSS - there are many other uses of bug reports for making non-FLOSS software but the ones on flosshub have to have something to do with FLOSS.