Linux/Apache/PHP & Windows/IIS/ColdFusion

Currently in-house our intranet is made up of Windows NT, IIS, and ColdFusion. We've also settled on MS IE as our standard browser, and use advanced authentication for logging into the intranet. This provides employees with one click access to the intranet without having to manually and physically login. We've been tossing around the idea of switching our Intranet to Linux, Apache and PHP but we would then lose that Advanced Atuthentication process, no? And to even complicate it even a bit more, if accessing the intranet internally through the network (a combination of Novell and NT) nobody should be forced to login (it being an automatic process) but if they access the intranet externally though the internet they have to be prompted for their normal network login information. Are my managers smoking crack, or do the advanced developers here think this is do-able? And if so, where could I find more information on setting this all up?