To put a bit more meat on Teiva Boy's answer:
1) The Backup Exec services hold ownweship of the tape devices so won't be able to share with CA
2) if either product uses the same IP ports as the other (I,.e NDMP for instance) then you will see another conflict - which could affect servcie start and/or the communciation of both media servers and remote agents
3) File System Filter drivers can cause conflicts between backup products too - this could potentially affect media servers and remote agents.and as a worse case might cause instability issues.
Also be aware that if you do a full backup foof Exchange or SQL with one product and then try and run an incremental backup of the same databases with the other product you will probably get errors too - this will affact side by side testing slightly.