My understanding is that selection for away games is no longer based on seniority (meaning 1/C get first chance to sign up) as it was in our day. Now, I think it's first come, first served after the signup period starts -- a current mid can correct me if I'm wrong. Doubt if plebes can attend as it's still first semester and typically they want to see a set of grades before they let plebes leave for a WE plus.
In terms of ND, my guess (and it's only that) is that they will fill the plane. If there are extra seats after the mandatory folks (team, etc.), then it MAY be opened to other mids. However, it's incredibly expensive and USNA doesn't have the budget to pay for hotel, etc. So, hard to say if mids will be able to attend.