However, just because one can SEE it on the My Calendar App on the phone, does not mean that the schedule/task/etc. Of course, on the My Calendar App ON THE PHONE, one can sync other calendars and other calendars will appear on the My Calendar App so you can see other calendars on your phone, while using the app.
However, there are some apps that connect exclusively with 'My Calendar'. That probably does work, functionally, for most people.