As mentioned above if this is using a BES there is a lot you can manage through the BES where it comes to DLP.
As noted above DLP for Mobile does not support Blackberry however the email will go through your corporate mail system and then flow through Network PRevent for Email if you have it in place and then block email.
There are other things you might get as well through the BES. The last time I worked w/ DLP and BES I was catching web traffic through the BES as well so Network Prevent for Web could be used for blocking the web traffic (not quite sure how that was setup but it can be setup)