I don't get it. There's no environmental gain in popularizing electric cars when they are inefficient, so what motivates the Transportation Department? I also don't understand what the significance of mpg in this context is. Electricity doesn't come in gallons. Subsidizing producers for meeting arbitrary criteria also doesn't make sense.

So, to me, it looks like someone decided to subsidize electric car manufacturers, and just needed an excuse in some legal framework. There might be a scandal there (e.g. bribes), but 6.67 factor ain't it.