It'll be on a rolling basis. I do believe those that submitted early will be looked at first. In your email, it states expected announcements by mid-February. I sure hope it is before then. The wait as a parent is excruciating
My DS is still awaiting news from the USCGA, USNA, and USAFA. He did however already hear back from the AFROTC and he did get a 4 year Type 7 scholarship. So, Plan B is addressed.
My DS got that USCGA notification email on 4 JAN 17 and he hasn't heard back yet. So, if you got yours yesterday, then I would give it a few more weeks than where my DS is.
In our case, we received that email a little short of two weeks after we submitted the application, but we got the final decision about two months since the application was initially submitted. (Application submitted beginning of October, email came mid-October, final decision came early December.)