Training contract starts first day of training.
It doesn't matter whether its enforceable or not, its your word. You've signed a promise that you realise that the training they're paying for costs money and that you will stay for at least a year to let them recoup the cost. Leaving before it expires might not cost you financially, but Eagle isn't the only company that looks down on ignoring a contract you've signed. I've been told that southwest frowns strongly on it as well.
A man's only as good as his word.
If I were you, I'd hold out for Pinnacle. QOL is everything, and colgan just doesn't deliver in that department. A union is on its way, but that'll take a couple of years before a contract is actually in place and making things better as far as scheduling, commuter policy, etc.