I know that nothing is guaranteed until I'm actually assigned a language, but what are my chances of getting the one that I want. I have a BA in Mandarin-Chinese and would really like to keep it once I arrive at DLI (I'm in DEP at the moment until I ship out for BC March 16). What are my chances of getting Chinese?

If you have a BA in Chinese you can probably convince them to give you Chinese even if there isn't a class immediately available for it. Just make sure to let them know. Don't let them tell you no.