Yes, the Provisioning API works with OAuth 1.0 and 2.0. See the docs and necessary scopes here.
If you just need all users in the entire Google Apps instance, use the retrieve all users in all domains API call and then filter out users with isSuspended = True
.
If you also need to filter the list down to users under a certain organizational unit (OU), use the Retrieving An Organization Unit's Immediate Sibling Users API call also and then filter down your list to users who are in the OU and are not disabled.