If they did file bankruptcy that doesn't mean any station would ever go dark, I think just about ever major airline (except Southwest) has been through bankruptcy at least once, along with GM, etc etc.
What would happen is the creditors would take a 'haircut" on what is owed, the stock holders would take a "haircut' by dilution of shares (creditors would probable end up with a % of the company),,,but Clear Channel would still be Clear Channel.
As David said, the outdoor division isn't small change, its worth a LOT of money (its amazing the cash flow an outdoor company can make)
The problem with most of the larger groups today is simply they bought stations at crazy prices, the multiples being paid were too high, and now it becomes hard to impossible to service debt.
Clear channel and Cumulus don't fire people because they enjoy it, they are trying to cut cost in an effort to service debt,,,if you overpay for any business, you have to find ways to increase revenue and/or cut cost,,,unfortunately but true