It says in the ts&cs on the page that you register interest that you need to use the new live app. I think they will be testing it with the new event. But you can only get into the app with the code you get from TM
I looked at that, and I think that's where the tickets will be delivered - didn't seem to be anything much going on in there when I downloaded it yesterday. The email I got came via the regular Coop app, and asked me to register interest for the ticket sale on 1 April. Previous presales have all been accessed in the regular app.
For Android it's here https://play.google.com/store/apps/details?id=mobile.appWeCS9BXzZa