being able to access shared calendars in powerapps is a highly requested feature for my use of an internal communication app
Being able to access shared calendars in PowerApps has the possibility of many different use cases. In my case I would use it to display our Global Holiday calendar. This has the company paid holidays in it for all offices of our offices.
I would set it to show the company holidays for the employee viewing it but with a drop down selector where they could choose any office (country) and see the paid holidays in that location as well. This could be embedded on a page on our intranet.