Hi everyone!
From our experience with E-CAS with London is that it doesn't change often, or at all!
It still says "In Process" for my husband's application and his passport has already been requested.
Also, if you provided your e-mail or not, every case is different. My husband was contacted by e-mail AND post on various occasions. For example, when London notified him that an interview was required, they sent it in an e-mail. When they set a date for his interview, it was by post. When they requested for his passport, it was also by post.
It's unpredictable and each time it's different! I know other people who had ALL correspondence via e-mail and others that had all via post.
Good luck everyone and I hope this helps a little bit!