Pretty much any consumer smartphone, including BB's, are traceable/monitorable. This is what all the recent hubbub was about in certain countries (ie India, Pakistan, various Middle East countries, etc) where they were pressuring RIM to provide access to customer communications for monitoring purposes.
The most secure communications on a BB is if you are running a Blackberry Enterprise Server, which allows the operator to set strong encryption and enter their own unique encryption key which encrypts content both in transit and on the devices themselves. THAT is the encryption that RIM has consistently stated they do not have a way to decrypt. If they were to put a "backdoor" in BES, then it would ruin one of the primary reasons companies run BES servers in the first place.
So if a national government wants to monitor BES users, basically they have to invoke state security laws and compel anyone who runs a BES to give them access in some way. I don't know if there's a common way of doing that, whether there is a special 'hook' in BES that allows external monitoring, or just have the state govt compel BES users to hand over their encryption keys to the government.
But BES-encrypted BB communications are very difficult to intercept without that access on the server side. BIS and BBM communications on the other hand: don't get too over-confident about those. RIM has made agreements with national governments all over the place to provide access to those communications.