I had opportunity to work on SoGo Connector for Thunderbird in order to correct and enhance it :
The correction was related to a sync problem with IceWarp server, because of an info missing in the CardDAV spec (how to handle a specific empty response) (http://www.sogo.nu/bugs/view.php?id=2311).
And the enhancement was quite interesting : I added periodic sync and notifications ! For each remote addressBook, you can define sync¬ifications properties.
Here is a screenshot :
I sent the patch to Sogo devs (http://www.sogo.nu/bugs/view.php?id=2393). I hope both patches will be integrated soon.