In 2.2.0beta2 when you enable dictation it works fine if you do not have outgoing caller id set in the extension setup. If you have outgoing caller id enabled in the extension setup you get a message saying that the feature is not enabled. Remove the outgoing caller id and it works fine.
This sounds like a similar bug/problem with ARI regarding recording calls. If you have outgoing caller ID set with the trunk settings, ARI will not place your calls in the monitor listing under the correct extension. It will still record calls but you will need to get to the recording with winscp or something like that.