The Verge is reporting from the BUILD conference that Microsoft has indeed been considering the rumoured Notification Centre for Windows Phone 8, but was not able to implement it in time for Windows Phone 8 RTM.
Microsoft’s Thomas Fennel, a program manager, responded to a question from the audience about its absence by saying:
“Because we ran out of time. It’s very important to me… we get tons of feedback from developers that they want something like that as well. I promise we’re thinking very very hard on that one.”
Live Tiles, which normally show missed notifications for apps considered important enough to pin, is usually cited as a good substitute for a notification centre.