Based on the code you show, that they tell you to use, they
are just tracking the image via their server logs.
Anytime someone accesses something from your site, it is
logged, including all information your browser will provide to it
... such as IP, estimated location, domain, etc etc etc
Nothing they are using in that example points to a
dynamically tracked image or specialized image tracking service.
HOWEVER, you can do it by creating a script that returns an
image if you don't have the ability to parse your server logs.
The script could be as simple as one that returns an image
based on criteria provided, or as complicated as a script that
generates it's own image on the fly.
However you do it, you would simply have them access the
script as <img href="
http://yourserver.com/thescript.cfm?id=3456">
In this simple example, a CF page is written that takes teh
URL variable of "id" and uses it to pull and return an image to the
user.
It would be up to you, then, in this same script, to analyze
the cgi variables sent back to your server. There is a fair amount
of information you can generate using the CGI variables. A search
of "CGI" in the CF help will reveal how to use them.