Inquiry about multisite use plus events

I’m not 100% sure of how to explain this, I’ll try my best.

Let’s say I have a multisite WP installation, site A, B, and C. (Doesn’t even have to be multisite, just separate sites that I would have access to.)

Site A is the information hub for all related businesses.
Site B is a business with their own calendar of events.
Site C is also a business with their own calendar of events.

I would like Site A to pull information from both of these sites and display it on a single calendar. Plus geolocating viewers to what is near them or not (such as what Events already does).

Is this even possible? I’ve gone over a few possible ways to do database information with this but I can’t seem to find a solution. GD’s Events add-on would be the best option for this, as Site A would have them displayed on a map (hence the reason for geolocating) but Sites BC would only display a calendar/list (like the GD Event widgets do).

I just don’t know if it’s even possible to share the information on back end, or if there is a way to share from front end.

Please direct me however you feel is necessary. I know it’s custom work, and I will find a developer if I need to, I just don’t even know how to explain this to someone. Since I’m not even sure if it’s possible I wanted to check with the GD team before pursuing a developer.

I can also give a specific example as to what I’m doing, the particular business type if it helps.