Can't believe that Apple have screwed up so badly. Well actually, I can. They are always doing dumb stuff like this which shows how little thought they put into everyday functionality.
Of course you should be able to select which calendar(s) appear in the notification center. Otherwise, why would you even want to have separate calendars? Apple have not thought about how people use multiple calendar functionality. Typically, the user will have a calendar with which to plan their daily schedule, and other calendars with which to plan and arrange unrelated things. For example, like the poster below, I have multiple employees each of which has an appointment calendar. I need all of these on my phone in order to be able to take bookings for them on the fly. I don't need to see their appointments in the notification center, just my own. It really is quite ridiculous that Apple have persisted with this stupid design decision throughout the whole beta testing period and I have little doubt that beta testers told them time and time again that this was a bad idea.
Any doubt as to whether or not the user will want one calendar or multiple calendar notifications? GIVE THEM A CHOICE. It's as simple as that.
Another potentially great idea RUINED by Apple's incompetent design teams, who apparently don't think about real world situations.
In a similar way, they failed with the lock screen notifications. As soon as you unlock the screen, any notifications you had disappear from the lock screen, so they only appear there when you first get them. This completely and utterly ruins what could have been an incredibly useful feature - to be able to see an outlook of your current notification status without unlocking the phone. I was really excited about this, but true to form, Apple screws it up like the absolute geniuses they are.