update: It seems that I can see shared calendars as long as I have created them by myself. After creating a new google calendar Jolla's calendar app shows new calendar in "Manage calendars" view.

It still does not show shared calendar created by my friend. I tested how it works with Ubuntu+thunderbird and android+S planner combinations and in both cases I can see all calendars I expect to see. I also verified calendar configuration in https://google.com/calendar/syncselect.

ssahla, thanks for the links. Unfortunately those did not solve the problem.