if browsing the web is allowed, you might consider a web-based client. iow a java applet on the web somwhere that acts as an irc proggy. I allowed friends to use an irc-cgi gateway on my webby for that very purpose. beats having to install software and all that
aha, that's the trick. iirc it has to run on someone's webserver and you connect to it with your regular browser. what you see is a form [or something like it] that gets updated in a constant data stream. it looks very much like your average irc client and can do just about everything your average client can.
The work machines use the RM filter to block out offensive words and all other shit they dont want you to see. CGI:IRC is just a cgi script and is able to connect no problem. There is no blocking of cgi at my work as far as I know.