Cloning or just plate theft only works if you put the plate on the identical make, model and colour of vehicle, as many ALPRs are also quantifying the traits of the vehicle and a non-match raises a flag and will likely get extra scrutiny.
Maybe it's hard if you have a classic car with an unusual paint job. Not so hard if you have a white Toyota.
Or, if you want to be organized, you run around with plate readers and log make/model/color/number and then sell that data.