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You can see a list of supported signatures here:

http://wiki.ros.org/roscpp/Overview/Publishers%20and%20Subscribers#Callback_Signature

With regards to multiple nodes with const boost::shared_ptr< nav_msgs::Odometry> callbacks, each node would perform its own independent deserialization of the ROS message coming in on its socket connection to the publisher, since nodes are independent in that sense. Different nodes are not separate threads, they are separate processes, and ROS doesn't (natively) support any inter-process memory-sharing type of schemes.

According to roscpp spec, if you had separate threads in one node both processing a callback like that, because you don't get a ConstPtr (const boost::shared_ptr< const nav_msgs::Odometry>), each callback would actually get a deep-copy of the data under the hood, in case the callback tries to modify the contents of the odometry message.

As far as the exception you're getting, there's hopefully a more reasonable explanation that's due to your client code. Feel free to link to a gist or something. Otherwise if it's something more insidious, it should definitely be reported as a bug.