It seems Rutgers doesn't think the Big East can legally hold them to the buyout provisions of the conference bylaws.
Their argument: the Big East hasn't held anyone else to the provisions (Pitt, 'Cuse, TCU, WVU). I'm no lawyer, but that sounds like a good argument to me. My guess is that Rutgers' motivation for doing this is more about the 27 month waiting period. Per Big East bylaws (again, not a lawyer) it looks like Rutgers' exit fee is only $5 million. (See pg 23 here.)
This buyout legal battle fiasco has become part of the conference realignment shuffle. Cost of doing business, as they say. These begin to look more and more like legal formalities than true battles. The Big East, in particular, has demonstrated the emotional stability of a jilted lover. "If you don't want to be here, go ahead and leave," they seem to be saying in each of these legal battles.