She told me that all of the economy fares, including promo were y,b,m & h.
Y,B,M and H are the most expensive of coach fares; those are all upgradable with miles.
Here's a summary of what I've found:
First & Business Class J, C, D, I
Full Fare Economy Class Y
Economy Class B, M, H, K, V, T, Q, X, W
Discount Economy Class A, N, L, O S?
Per this page:
http://alitalia.com/EN_EN/millemigli.../crediting.htm
Only R doesn't earn miles