Boomtown has published a Q&A with Cryptic Studios' Jack Emmert, in which the lead designer answers several questions about the upcoming City of Villains. Here's a bit to get you started:
Q: How exactly is the PvP between villains and heroes going to work?
A: There are several different reward systems in place. I've already mentioned base raids, so heroes and villains can raid each other's bases on specified times to seize the items of power. You gain those by stealing them from Rularu the Ravager in the Shadow Shard. After you gain one of these items, other people can try to take them away from you again.
Another form of PvP will be in the zones Siren's Call, Bloody Bay and Warburg. Each zones has a mini-game related to PvP. In the case of Siren's Call there's an on-going war between Longbow (the forces of the heroes) and the Arachnos, the villain group. Players are then assigned different territories, which they must take over. In Bloody Bay players are trying to collect pieces of a meteorite in order to gain the ability to summon extra-terrestrial creatures. So in each case PvP in a zone is a means to and end, but that's not all - players also gain experience points for taking out opponents and they also gain something called reputation, which also has some inherent rewards. With higher reputation you can unlock some bonuses, with lower reputation some penalties will occur.