Each event on a Teamup calendar can be shared via the Share menu. One of the options is Share > Teamup.
This means sharing an event from one Teamup calendar to a different master Teamup calendar. If you have multiple Teamup calendars on your dashboard, you can share a copy of an event from one master calendar to another.
Any calendars you access via shareable calendar links can be added to your dashboard so you can share events between all the Teamup calendars you use, as needed.