MSE will sell the land/arena/practice facility, so that's probably a good chunk of the money they'll need, if not all. It won't happen quickly, but it's some prime land when development picks up. Bottom line is, if they really want out, they could just deed the land over to the city as payment in full. I'm not sure they do that, as the land is probably worth more, but it's an quick and easy way to pay off the city.
Also, They don't owe the full $70 million. I don't know what the princiapl balance is now, but when things were going well, financially, MSE actaully was ahead in payments on the loan. After paying for 10 years, the principal has to have come down a decent amount.
Breton mentions none of that, of course.