I'm not familiar with Compellent but others that do similar work allow you to take transaction log backups along with their backups and allow for restores through the same.

That all being said though there are reasons to keep the Red-Gate backups as well (or any type of SQL backups) some of which include the ability to restore without having to go to your probably already overworked SAN admin to do basic recoveries or to copy data to another environment, etc. Before throwing all other backups out I would sincerely look at all processes where backups might be used and then make sure that the SAN admins are going to be willing to support those activities.

One other thought too, but if you are doing any replication I would make sure that they support the KEEP_REPLICATION option as part of their restores.