Hi Vanessa,
Interesting questions!I’m so glad you’re checking The Events Calendar and I hope it’s a good fit for this project.
I’m afraid that back-and-forth syncing is something the calendar doesn’t support very well. We do have an add-on called iCal Importer and that will fetch new (and updated) data from a hosted .ics file/feed and import those events into The Events Calendar on a scheduled basis. That part is perfect.
What’s not perfect is the communication from The Events Calendar to the outside source. In other words, iCal Importer will add a valid iCal feed to The Events Calendar that can be used by outside applications, but it is up to those outside applications to fetch the data on their own and decide whether or not the information is new or updated.
That said, I’m not sure this is the silver bullet you are looking for, but it is theoretically possible depending on the functionality of the applications pulling data from The Events Calendar.
Does this help answer your questions? Please let me know. 🙂
Cheers!
Geoff