The system you are looking for is called EXCDS or commonly referred to as "Exceeds".
It is used in a few of the terminals control zones in canada (at least Toronto and Calgary) and in the new pearson tower. Nav Canada is in the process of introducing it in other places but they have their plate pretty full now so it will be a while before its totally implemented across the country.
Here are a couple of useless links to EXCDS:
http://www.navcanada.ca/contentEN/co...gedge/iids.asp
http://www.navcanada.ca/contentEN/ne...operations.asp
http://www.navcanada.ca/contentEN/ne...atoontower.asp
And i think a company that has built it or something:
http://www.activeideas.com/AIdev_200.../products.html
Sorry not much help..if you contact the latter i am sure they can give you some info, but their website is full of dead links
G