Is it possible to use mixed LDAP and local Drupal authenticated users on the same site
Any accounts created through LDAP will have access to the site. Alternatively you can create local Drupal users that also have access when using mixed mode.

For instance I work with sites where I have LDAP credentials that allow me access to all the sites. I also had a local Drupal user for one or two that have different credentials and I can log in with either (same email).

Depending on what modules you are using to facilitate this process they may even create a local user for each LDAP user (not sure if they all do this or not). This comes in handy when experiencing LDAP issues as you still have access to your site/s.