I was happily sharing my Lightning (Thunderbird plugin) calendar by copying the calendar-data/local.sqlite file between home and work computers, but an update to Lightning made that suddenly impossible; even with the correct sqlite db in place, Lightning would show a completely empty calendar. Eventually I figured out what to do:

• Shut down the Thunderbird which has the problem.
• Install sqlite and sqlitebrowser (from the repos).
• Open the db file, and find the cal_id field value in one of the tables (such as cal_alarms). Copy it somewhere.
• Open prefs.js, and search for any entries with "calendar" in them. There should be a block of them, and they'll all look like this:

  user_pref("calendar.list.sortOrder", "5d27f585-81fb-4f2c-8686-cf28b7ee5a0a");

• Replace the id value (the long GUID) with the cal_id from the Sqlite db. Save, then start Thunderbird.