Junk bonds do sometimes pay off. Some city and state governments will be able to honor these pensions. Therefore, it shouldn't be construed as fraud. A seller of junk bonds is not guilty of fraud. It is simply a demonstrably poor strategy to rely on them 100% and investing entirely in a single entity. I put the bulk of the blame on the side accepting a strategy that essentially amounts to investing entirely in junk bonds in a single entity.
A small, sustainable pension funded by the public is fair to offer if desired, plus private diversified retirement accounts with both employee and employer contributions for anything larger than a basic stipend.
Why should pensions be financed by bonds, junk or not, instead of through collected taxes? Wouldn't the fiscally responsible thing for municipalities be to figure out what your obligations are and then adjust the tax rate accordingly so you bring in enough to fund your obligations?
The problem isn't pensions. The problem is when politicians under the thrall of Grover Norquist decide to start deferring payments instead of requesting an appropriate level of funding that will meet the city's obligations.
Cities like Detroit never seem to have a problem finding money to pay for stadiums and other multimillion dollar business tax concessions. You'd think they'd be able to handle pension funding they had a had in negotiating.