I had to do the following to display a X terminal remotely.
This initial Solaris install was done with the X packages, so I did not need to install anything specific for xauth or xterm.
$ ssh -X root@t41-ldom2 Password: Last login: Wed Jul 10 10:07:30 2013 /usr/openwin/bin/xauth: creating new authority file /root/.Xauthority Oracle Corporation SunOS 5.10 Generic Patch January 2005 root@ldom2:~# /usr/openwin/bin/xterm
First install a couple packages. If you previously installed more of the X packages you might not need these two.
root@ldom1:~# pkg install pkg:/firstname.lastname@example.org root@ldom1:~# pkg install pkg:/email@example.com
Login with -X
$ ssh -X root@t41-ldom1 Password: Last login: Wed Jul 10 10:11:49 2013 Oracle Corporation SunOS 5.11 11.1 September 2012 You have new mail. root@ldom1:~# xterm