Diversion contracts are usually a 'we will handle you as and when we can' type thing, they don't state a specific time frame or man power levels that an ordinary contract would state.
While handling agents have a say in whether they get a divert or not, they can't turn it away by themselves. Usually they persuade the airlines ops, or airport authority to turn the flight away but if they insist on coming there's little you can do to stop them.