If the company cares about the AUP that they have, the you will most likely be caught. It probably is just a matter of someone get around to it.

If this communication is vital to your work, your group should write a proposal to your manager with what you think your group would need to work effectively. If your proposal has merit, then I'm sure that some SECURE alternatives could be created by the IT in your company.

Spending all this time trying to get around the rules will most likely come back to bite you in the ass and give you lots of spare time to chat with your friends....from home.

Just my 2 cents.