I found this post Ryan Hadley a few days ago, which I got working with a little bit of time, I noticed that Thunderbird was displaying all-days events oddly, so I checked the VEVENT info being generated & tweaked to work correctly with Thunderbird/Lightening. I also dropped in the URL of the event in OWA & fixed it for situations where there are public & private names for the OWA/Exchange instance, handy when you want to go and amend an entry etc.

Hope you find it useful. []1

Exchange2ICS.tar.gz