I'll be eyeing this since I'm looking for a solution to the same problem but I'm working on other things at this moment so I haven't been able to look into it in depth yet.
Did you have a chance to look at https://www.calendarserver.org/ ?
Or Davical http://www.davical.org/
I'm using davical (http://www.davical.org/) installed on a server. I have thunderbird (with lightning, work and home) and my iphone all synced to the same calendar. I also have my wife's thunderbird and iphone synced to her calendar, and we can see each other's calendars, too. We can also post events to each other's cal's as well.
Works great to make sure we know each others schedules.