As soon as I finish finding and squashing all these bugs I'm finding I plan to build sync tools to let you easily import outside calendars into private nip-52 events too.
Discussion
I didn't look closely, but it looks like the bookings only have encrypted content? It might be better for hiding metadata to use nip 59 gift wraps. I'll keep playing with it and let you know if I see other thing
That's a bug I'm actually working on now. When I moved from my own setup to using mkstack a lot of the booking logics broke down so I'm more or less troubleshooting with individual ones to find them.
They should be using gift wraps though. Unless you manually set to public, the plan is to make all 922/923/925 events be gift wrapped which is why I'm using a new 927 to still manage busy times.