Curious about

What is the name of your state? Arizona
I'm just curious about hiring practices... When I accepted the position I am currently in, the city offered a 1 year vestment in their retirement program. Since in my position, I may move periodically, it was this benefit that got me here. The salary was only insignificantly higher than my previous employer. Three months later they converted to the Arizona retirement system that requires 5 years and only then a 50% vestment and forced us all to participate by refusing to continue the previous benefit. Shouldn't we be offered the option?

Because you are a public sector employee, unique rules apply. The odds are what you describe is completely legal but only someone intimately familiar with retirement plan administration for your municipality and State can advise you. These types of changes typically are intensively reviewed by the city's attorney and retirement plan administrator as improperly monkeying-around with a publicly funded retirement plan is the kind of thing that costs people their jobs and sometimes can send them to jail.

FYI - If the city's retirement plan was discontinued in favor of the State plan, which appears to be the case, then there were no options to offer you as the prior plan no longer existed.