Don't forget the copper MICS went from DR1 - DR5.1. you can not forward a call with that vintage. The fiber MICS started at RelT1 software and goes to 7.1. On the fiber MICS call forwarding outside the system started at Rel4.1. There is a faq on setting this up, I used it and worked perfectly. As exmogger mentioned you need to do some programming, having at least 4.1 sw and a fiber MICS.
You can use "line redirect" to forward DID's or telephone lines, but in my opinion it doesn't work well.