It's not necessarily a fraud. The key is it only works in cases where the fair market value of the house is below the value of the mortgage. In that case, the city only has to pay the FMV. Now, there is always going to be some question about what is actually the FMV of a property. But this is true regardless of whether the city is in cahoots with a property developer who wants to put up some expensive shopping mall where single family homes once stood, or in this case where Richmond is proposing to seize by eminent domain houses which are underwater.
Why are the banks against this? (1) they believe they could get more at auction than the FMV determined by the eminent domain process, and (2) the seizure happens at a time outside of their control, where as the bank might be holding off on the foreclosure process since if they were to actually foreclose on the property, and discover from the auction that they could recover significantly less than the mortgage, they would then realize a loss which would screw up their capital holdings.
Either way, as far as the homeowners are concerned, they are effectively going to be foreclosed against. The only difference is that they will be offered a chance to continue to live in the house, and pay rent (which might or might not be at FMV; it's not clear from the description). Maybe it might be a rent with an option to buy, but basically the main goal of the city is to preserve the neighborhood instead of letting speculators buy the house at foreclosure.
So I wouldn't necessarily call it a scam. Will the banks lose out? Probably. But I don't know that they would necessarily lose out that badly --- that is, unless you don't believe that people who lose their houses due to eminent domain when a city is enriching some real estate developer isn't paying FMV to people who are turned out of their homes to build a shopping mall or a new stadium....