Yes, you can reuse bubble sheets from another test. However, you won't be able to upload the sheets using email upload. You'll have to upload the scanned sheets through your dashboard and ensure the 'Force upload' option is checked.
We use the QR code on the test sheets to track which teacher and assessment the bubble sheet was printed from. The 'Force upload' option will override the QR code and put all sheets in the same assessment.
Image: Force all responses check box when uploading sheets.