Yes, after what you have written I have checked my new application number. It starts with the three digits which are same as the school's student number initials. My old application number's first three digits were different. I guess they have given me a student number, but as you said it may not imply an acceptance.
I have still not heard from the only school I have applied. However, today, when I have checked the application status webpage, I have noticed that they have changed my application reference number. They did not update the status info though.
Why did they change the reference number? Is it a good sign / bad sign or no sign at all?