Thanks, Casey. Our previous developer coded these, and alluded to the fact that at some point there was some documentation that showed them to this method of cross-site shared widgets. Neither they nor I can find where those docs went.
The former devs actually got cross-site Calendars working really, really well in Events Calendar 2.9. Unfortunately, we were stuck in a place where we were unable to upgrade to a current version of Events Calendar Pro as a result. Our hope is that we can get this working again for 3.6+, as we’re relaunching our university website very soon and Events Calendar features quite prominently on it.
This first bit of code is what gets inserted into functions.php in our theme: https://gist.github.com/electricbrick/fcc7d0fe97d41bd62faa
The second block of code is its own file, tucked away in the theme’s /lib/ directory:
https://gist.github.com/electricbrick/8e7827fae608ed2b42cc