I don't think ipp2p blocks ICQ, but it is definitly good to block filesharing programs.  Start by looking here:
http://www.google.com/search?q=iptables+block+icqInstead of "iptables -A ???" though,  you can test the rules with "iptables -I ???" - I think that works better for testing, and you can see what will work immediatly.  
Then you just create a custom template in etc\e-smith\templates-custom\etc\rc.d\init.d\masq\ called 38ICQ with the rule that works (you can use -A there).  
Restart masq with:
etc/rc7.d/S36masq restart
...to see if your rule is working.
Let us know what works for you 
