I am looking for a way to get the instance information for a given EC2
provisioned slave node at launch time and use this information in script prior
to running jobs on the slave. The specific use case is to launch an ssh session
from the Hudson master to the slave and open one or more reverse tunnels from
the slave to the master's network.

I looked at this just a bit. It doesn't look like the com.trilead.ssh2 lib can
do tunneling. I think a good way to implement this would be to expose the
properties in the the typica instance class (dnsname, etc) to the environment
and provide a shell script (similar to a build step from a job?) that runs on
the hudson master. That script could run ssh on the master and connect to the
slave using the exposed properties.