CAS is capable of delivering some GTED attributes for the person logging in to Drupal, as part of the login process. This means you don't have to configure and maintain an LDAP module nor manage an LDAP service account (read: no need to keep up with an expiring service account password).
While Georgia Tech's CAS service will provide authentication for any site within the ".gatech.edu" domain, by default it won't release any attributes. You'll have to request what attributes your application needs by filling out the OIT IAM Data Steward Request Form (this is the same web form that you use to request a GTED LDAP service account.) Make sure you specify CAS authentication and whatever data you need under Data Request.
Once that has been approved and CAS has been set up, configure Drupal to talk to CAS just as it's documented here on previous pages, except for the CAS Server Version, which needs to be set to SAML Version 1.1. If the user's email address is one of the attributes you're requesting from CAS, then you'll want to leave the email address field under User Accounts blank.
Now, under the Attributes tab, select the CAS Attribute Tokens button (not the "LDAP Attribute Tokens" if you have that). It should show you a list of attributes Drupal is getting from CAS. You may have to log out and log back in. If you don't see the list, you may have to work with whoever handled your data steward request, sometimes these things take a bit of tweaking to get right.
Still on the Attributes tab, select the Settings button. You'll want Drupal to Fetch CAS Attributes "everytime a CAS user logs in" because, well, people's data changes all the time. You'll probably also want to always Overwrite existing values from attributes, to make sure Drupal doesn't store any old data. Under CAS ATTRIBUTE MAPPINGS, specify "[cas:name]" for the Username field and "[cas:attribute:email_primary]" (assuming you requested that) as the E-mail address field.