According to the Marshalls, A moderator, and MadMat
CatC 1980 -> CatB 1985 -> 1990 but caps at 1995
Marshalls also say that availability bonuses won't be in the game. However I wouldn't believe them because a lot of those marshals are just elitist players who get their own subforum and the fact that they aren't devs.
The Devs have yet to officially confirm the removal of spam bonuses though.