Hi,
Since Internet Explorer Mobile is baked into ROM, a given OS release will always have the same version of IE Mobile installed (there is currently no possibility for an end user to upgrade etc).
However it is more than matching up WM 5.0, WM6.0, WM 6.1 etc, as there is also the potential for the browser version to change between more minor OS upgrades (called Adoption Kit Updates or AKUs).
What is your need to match up browser and OS releases?
If you are developing a website and need to alter your HTML / Javascript content to suit the capabilities of individual browsers you are in general best to use the browser client identification.
Hope this helps,
Christopher Fairbairn
Visit my blog at
http://www.christec.co.nz/blog/