Is there a way to add someone else's calendar to my screen, ie., sync calendars to share events with only one other person?
There is not. The Canvas Calendar is designed for interaction and accessibility within classes you belong to.
To see information from multiple Canvas calendars, you'd have to have someone email you their .ics file, and add them to an external calendar tool, such as Google Calendar, or iCal. However, this will not allow you to push changes onto the Canvas calendar.
Retrieving data ...