I'm pretty sure this is the first year the NBA has kept these stats officially. +/- is the difference in points scored by the team when a player is on the floor. For example, if Lebron James plays 40 minutes in a game and the Cavs score 15 more points than the Bucks during his 40 minutes on the floor, his +/- for that game is +15.
BA stands for blocks against. It shows how many times a player's shot is blocked during a game.
The first (and only?) preseason matchup to be broadcast on NBA TV is tonight's Grizz/Heat game from San Juan, PR at 19:30 Central. Hoops or Smackdown, hoops or Smackdown... While I'm at it, here are the other national preseason games: