If it is a non-internet facing site, your choices are limited. As the article mentions, you could use Microsoft's UAG (f.k.a. ISA) to gain access. I have accessed one this way before. The other option is to connect to your intranet via VPN. Some smart phones have VPN clients built in. Some VPN concentrators also allow web access (where you browse to a web page and a Java Applet or ActiveX VPN client is downloaded to the browser), but you will have to be sure your phone's browser works with Applets or ActiveX for this to work.
In summary, it boils down to two things:
1) You need a way to connect to your network
2) You need to be sure your phone and its browser supports the method you use to connect to your network