I've released v0.4 of matlab_rosbag, a library for processing ROS bags in matlab. In addition to some bugfixes the new version includes:
1) a class to work with the tf tree (transform queries, list frames, etc.) using stored tf or tf2 messages
2) ability to filter messages by time and get access to bag start/stop time.
3) Autocomplete paths to bags using ros.Bag.load()