We had a similar situation. Tape drives attached Backup Exec 2008 R2 server, got tired of their poor support switched to Veeam. What I did was:
1. Backed up the Catalog and Data folders on BE server in this KB article from BE: https://www.veritas.com/support/en_US/a ... TECH129826
2. Blew away Backup Exec server and installed 2012 R2
3. Installed Veeam, attached Qnap repository, installed non-exclusive drivers for our IBM tape drives added tape drive/library to Veeam
4. Installed Backup Exec on same server and used the steps in the KB article to move the Catalog and Data folders to new server so the new install of BE would have all the old servers Catelogs for the data we backed up to tape via BE.
Once the steps in the KB article are completed, verify your catalogs are still intact from the old server. Put all jobs on hold and shut off the BE services until if and when BE is needed to restore data from those BE tapes. We didn't have to change drivers for the tape drive to use the tape drive with BE. Just make sure no Veeam tape jobs are running when if and when you attempt to restore from BE tapes. We have successfully restore data for our file servers using old BE tapes using this method.