Numerous Titans got physically involved on the fourth episode of TNA. This would be with a month and half until the regular season, with active players that were expected to contribute to that season.
Personally, the Titans have every legal right to stop this, but there's about a 1-in-a-million chance of Pacman getting hurt in a fashion that would affect him over one year from now, plus he is rather lacking in the paycheck this year, so I see no harm in him participating.
I apologize in advance if this a bit late. No contest between Cena and Kane. It gets out of hand as Cena goes crazy and destroys Kane to try and give the illusion that he might turn heel (though we know that won't happen anytime soon).