You can use the Build Trigger API for this: Triggering and aborting builds - Bitrise Docs
The question is, where are those stored? If you store them on e.g. Amazon S3 you can download them in a new build, but if stored on bitrise.io as a build artifact then unfortunately you can’t access those right now (a build can only access its own files). That said we’re working on the API feature request, which will add functionality for this use case, feel free to vote & comment:
If you have any questions just let us know!